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Biomedical subjects

R Katz

Publications and source records attributed to R Katz.

At least 289 records · Page 16Linked to original sources
PubMed1978

Muscle reaction to passive shortening in normal man.

We have studied in 32 healthy subjects the EMG activity of biceps and triceps brachii, wrist flexors and wrist extensors, triceps surae and tibialis anterior, sterno-cleido-mastoideus (SCM) and splenius, during their passive shortening. A shortening reaction was observed more frequently in wrist extensors, SCM and tibialis anterior than in biceps and triceps brachii. The response appeared only when the joint reached a specific angle regardless of the starting point or the speed used to reach this position. During a muscle ischaemia which abolished the tendon reflex the reaction was not modified. During a joint ischaemia produced distal to the examined muscle its amplitude was strongly reduced. Our results support the hypothesis that joint receptors could play a role in its origin, perhaps through a long-loop reflex.

Adult↗
PubMed1978

High LET constraints on low LET survival.

Survival curves for biological cells irradiated with gamma rays (and other low LET radiations) cannot be properly interpreted without examining the implications of these interpretations for high LET radiations. The theory of RBE demands that the RBE of any high LET radiation field is at most one when the probability for cell killing as a function of the absorbed dose of gamma rays is linear or sublinear, for homogeneous samples whose radiosensitivity parameters are not altered during the irradiation. A contrary experimental finding strongly suggests that the experimental sample is heterogeneous. Violation of this constraint is not unusual where the survival curve found with low LET radiations has a well defined initial negative slope.

Animals↗
PubMed1978

Radiobiological aspects of supralinear photographic emulsions.

Nuclear emulsions of the Ilford K series, exposed to X-rays from 15 to 150 kVp and systematically underdeveloped, exhibit supralinear blackness--exposure curves ranging from 1- to 4-hit in character, and whose shape is the same at all excitation voltages. Processing can be so adjusted that the curve shape is well represented by the alpha--beta model, and matches an experimental dose--response curve obtained with hamster cells after irradiation with gamma rays. The effective grain size of these emulsions is 1.3 micron when normalised to unit density material for comparison with the radiation sensitive elements of biological cells. With fractionated exposures, response curves which mimic Elkind recovery are produced.

Dose-Response Relationship, Radiation↗
PubMed1978

Calculated yields and slowing-down spectra for electrons in liquid water: implications for electron and photon RBE.

Detailed Monte Carlo calculations have been carried out of slowing-down spectra and yields for a number of end-points for electrons in liquid water. These investigations were made to study differences in physical effects of different low-LET radiations and implications for RBE. Initial electron energies from 1 keV to 1 MeV were used, and all secondary electrons were followed in the computations unitl their energies fell below 10 eV. Though there are substantial differences in the slowing-down spectra at energies near and above the K-shell ionisation potential of oxygen, the energy spectrum of electrons at lower energies is found to be essentially independent of the initial energy of the primary electron. The number of events per unit energy deposited is also essentially independent of the primary electron energy. Based on these calculations, there appears to be little basis for ascribing differences in RBE for low-LET radiations to differences in physical effects produced by secondary electrons of low energy (less than or equal to 1 keV).

Electrons↗
PubMed1978

Clinical and pathological study of asymptomatic HBsAg carriers in Chile.

A clinical, biochemical, and pathological study was performed in 38 chronic HBsAg carriers. The study group is a part of 393 carriers found among 117 705 voluntary blood donors at the National Blood Bank, Hospital del Salvador, Santiago, Chile. None of the 38 carriers had a past history of illicit drug abuse, hepatitis, or work involving a high risk of hepatitis B virus infection. Ten individuals had a normal liver biopsy, 17 reactive non-specific hepatitis, one fatty changes, four chr onic persistent hepatitis, one aggressive hepatitis, two post-necrotic cirrhosis, and three alcoholic cirrhosis. There was not a close correlation between liver function test and liver histology. The most significant laboratory finding was the postivity of alpha fetoprotein in two cases. During the follow-up the two alpha fetoprotein patients presented a hepatocarcinoma 12 and 14 months after admission to the study.

Adolescent↗
PubMed1978

Prevalence of intrahepatic cholestasis of pregnancy in Chile.

The prevalence of intrahepatic cholestasis of pregnancy was studied immediately postpartum in 869 women from three distant Chilean cities differing in climate and food supply. Cholestatic jaundice of pregnancy was detected in 2.4% and pruritus gravidarum in 13.2%, without significant differences between the three cities. Every woman was then ethnically classified as predominantly Caucasoid, Araucanian Indian, or Aimara Indian. A significantly higher prevalence of cholestatic jaundice of pregnancy (5.5%) and pruritus gravidarum (22.1%) was found in Araucanians than in Caucasoids (2.5% and 12.6% respectively) or in the Aimaras (0 and 11.8% respectively). The prevalence of intrahepatic cholestasis of pregnancy in Araucanians increased directly with the degree of "ethnic purity." Recurrence of the disease in multiparous women was also greater in Araucanians (13.8%) than in Caucasoids (5.5%) or in the Aimaras (3.9%). We propose that an ethnic predisposition to develop intrahepatic cholestasis of pregnancy is present in Araucanian women and that the high prevalence of the disease in Chile is mainly influenced by ethnic admixture with this South American Indian (ethnic) group.

Adult↗
PubMed1978

Job longevity as a situational factor in job satisfaction.

This study investigates the relationships between overall job satisfaction and the five task dimensions of skill variety, task identity, task significance, autonomy, and feedback-from-job for employees at different stages of their careers, as measured by their length of employment on their current jobs, as well as in their current organizations. Basically, the analysis shows that the strength of the relationships between job satisfaction and each of the task dimensions depends on both the job longevity and organizational longevity of the sampled individuals. For employees new to an organization, for example, only task significance is related positively to job satisfaction, while autonomy has a strongly negative correlation. The study presents other significant correlational differences and discusses the implications of its findings for task design, as well as for managing new employees. Approximately 3500 respondents from four different governments--two metropolitan, one county, and one state--participated in the collection of survey data.

Job Satisfaction↗
PubMed1978

[Change in recurrent inhibition when standing in normal subjects and spastics (author's transl)].

In normal subjects and patients with diseases of the upper motor neurone, recurrent inhibition directed to soleus motoneurones was studied in three different postures: sitting (control situation), standing when leaning backward on a wall, standing independently without the support of a wall. In normal subjects, this recurrent inhibition was not modified when standing with the support of a wall, while it was enhanced when standing without such a support.

H-Reflex↗
PubMed1978

Treatment of chronic childhood asthma with beclomethasone dipropionate aerosols: II. Effect on pituitary-adrenal function after substitution for oral corticosteroids.

The effects of beclomethasone, dipropionate aerosol (DBA) (400 microgram/day) on clinical course, pulmonary function, and pituitary-adrenal function was studied in 34 steroid-dependent asthmatic children. Asthma severity was assessed by daily symptom and medication scores, peak flow measured three times a day, and weekly spirometry. Pituitary-adrenal function was evaluated by diurnal cortisol levels, cortisol responses to intravenous (IV) corticotropin (ACTH), and steroid responses to IV metyrapone. After 12 weeks of BDA therapy, 30 of 34 patients no longer required prednisone. Mean weekly symptom and medication scores and the number of attacks decreased significantly (P less than .01)). A significant improvement was demonstrated in the patients' peak flow (P less than .01), forced expiratory volume in one second, and maximum midexpiratory flow rates (P less than .01). Thirty of the 34 patients initially had abnormal metyrapone responses, 28 had abnormal diurnal cortisol levels, whereas only 14 had abnormal IV ACTH response tests. Although significant improvement was noted in the mean metyrapone and diurnal cortisol tests, only partial recovery of pituitary-adrenal function was observed in 20 patients, complete recovery in 5, and no change in 9. BDA was found to be therapeutically superior to oral steroids in the group of steroid-dependent asthmatic children and produced no serious adverse effects.

Administration, Oral↗