Search PubMed⌕ Search

Biomedical subjects

B Falk

Publications and source records attributed to B Falk.

12 recordsLinked to original sources
PubMed1992

Evidence that pepper mottle virus and potato virus Y are distinct viruses: analyses of the coat protein and 3' untranslated sequence of a California isolate of pepper mottle virus.

Pepper mottle virus (PepMoV) is a member of the large and complex genus Potyvirus, and is classically distinguished from other members of the genus by differential host range and cytopathology as well as serology of the coat protein and cytoplasmic inclusion body proteins. Here we report the deduced amino acid sequence of the coat protein of a California potyvirus identified by a variety of classical methods as PepMoV (PepMoV C). Comparison of the 3' untranslated nucleic acid sequence and the deduced coat-protein amino acid sequence of the PepMoV C isolate with those of PVY and other potyviruses indicates that PepMoV C is sufficiently diverged to be considered a distinct virus species. Thus, comparative sequence analyses of the PepMoV C isolate support earlier serological and biological evidence that PepMoV and PVY are distinct viruses.

Amino Acid Sequence↗
PubMed1992

In situ immunogold labeling analysis of the rice hoja blanca virus nucleoprotein and major noncapsid protein.

Ribonucleoprotein particles (RNPs) of rice hoja blanca virus (RHBV) were purified and used for electron microscopic analysis and antibody production. Antibodies made to RNPs specifically decorated purified RNPs. The RNPs typically showed characteristic tenuivirus morphologies. They were approximately 8 nm in diameter, mostly circular in nature, and exhibited branching and a high degree of superhelicity. When the RNP antibodies were used for in situ immunogold labeling analysis of RHBV-infected tissues, no specific structures were identified, but gold particles were distributed throughout the cytosol of RHBV-infected but not healthy plants. However, amorphous semi-electron opaque inclusion bodies (ASO-IBs) were abundant in cells of RHBV-infected plants. While the ASO-IBs were not labeled with the anti-RNP antiserum, they were specifically labeled with antibodies to the RHBV major noncapsid protein (NCP) and with antibodies to the NCP of another tenuivirus, maize stripe virus.

Gold↗
PubMed1992

Sweat gland response to exercise in the heat among pre-, mid-, and late-pubertal boys.

Sweating rate (SR) of boys is lower than that of men. To assess the association between the response of individual sweat glands and physical growth and maturation, three groups of circumpubertal boys cycled at 50% VO2max in a climatic chamber (42 degrees C, 20% relative humidity). Based on Tanner staging (pubic hair), 16 were classified as prepubertal (PP, Tanner 1), 15 as midpubertal (MP, Tanner 2-4), and five as late-pubertal (LP, Tanner 5). Population density (PD) of the heat-activated sweat glands, the mean area of sweat drops (DA), and the proportion of skin covered by sweat (%A) were measured by skin photography and computer-assisted imaging analysis. Other measurements included rectal and skin temperatures (Tre, Tsk, respectively), heart rate (HR), and total body SR. The rise in HR, Tre and Tsk did not differ among groups. Whole body SR was significantly higher in the LP group compared with PP (PP = 4.95 +/- 0.23, MP = 5.79 +/- 0.20, LP = 6.70 +/- 0.42 ml.min-1.m-2) (mean +/- SEM). PD was significantly higher in the PP group (PP = 128 +/- 8, MP = 97 +/- 9, LP = 74 +/- 9 glands.cm-2), while DA was higher in the LP group (PP = 5.47 +/- 0.59, MP = 6.92 +/- 0.47, LP = 12.83 +/- 1.41 microns2.10(4)). %A did not differ among groups. The calculated SR per gland was higher among the LP groups compared with the less mature ones (PP = 4.6 +/- 0.3, MP = 7.2 +/- 0.8, LP = 9.6 +/- 1.0 nl.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Thermoregulatory responses of pre-, mid-, and late-pubertal boys to exercise in dry heat.

During exercise in a hot climate, children have been reported to have a less effective temperature regulation capability, compared with adults. It is likely that the transition from a child-like to an adult-like response occurs during puberty. To assess the association between the thermoregulatory response and physical maturation, three groups of circum-pubertal boys cycled at 50% VO2max (three 20-min bouts with 10-min rests), in a climatic chamber (42 degrees C, 20% relative humidity). Based on Tanner staging (pubic hair), 10 were classified as prepubertal (PP), 13 as midpubertal (MP), and eight as late pubertal (LP). Measurements included rectal and skin temperatures (Tre, Tsk), heart rate (HR), sweating rate (SR), oxygen consumption (VO2), and forearm blood flow (FBF). Tre, Tsk, and HR increased with time, with no significant difference among groups. Relative VO2 (ml O2.kg-1) was similar among groups. FBF was consistently higher in PP compared with LP. In spite of the higher SR (PP = 4.9 +/- 0.2, MP = 5.7 +/- 0.3, LP = 6.6 +/- 0.4 ml.min-1.m-2) (mean +/- SEM) among LP compared with PP, the rate of heat storage (PP = 5.5 +/- 0.4, MP = 5.3 +/- 0.4, LP = 6.8 +/- 0.3, kJ.h-1.kg-1) was also significantly higher among those in the LP group. Three of eight LP did not complete the session due to high Tre, while two of the 10 PP were unable to complete the session even though the physiologic heat strain was not high. The results suggest that the transition from a child-like to an adult-like thermoregulatory effectiveness in a hot, dry climate may occur at a somewhat later stage, but not during puberty.

Adolescent↗
PubMed1991

Sweat lactate in exercising children and adolescents of varying physical maturity.

This study attempts to explain some of the individual variability in sweating pattern by comparing prepubescents and pubescents. Sweating rate and muscular anaerobic capacity are higher in adults than in children; thus we hypothesized that sweat gland anaerobic metabolism, as reflected by lactate excretion, might be higher with advanced physical maturity (PM). Lactate concentration in sweat ([LAC]sw) was measured at various stages of PM in boys who exercised in the heat. The subjects were divided into three groups on the basis of Tanner staging: prepubertal (PP, n = 16), midpubertal (MP, n = 15), and late pubertal (LP, n = 5). Subjects cycled at 50% of maximal O2 uptake for three 20-min bouts, with 10-min rest periods, in 42 degrees C and 18% relative humidity. Sweat samples were harvested, and population density of activated sweat glands was determined after each exercise bout. [LAC]sw during bout 1 was higher in PP than in LP [PP = 22.2 +/- 2.2, MP = 19.5 +/- 1.4, LP = 14.3 +/- 1.3 (SE) mmol/l]. In all groups, [LAC]sw decreased during subsequent bouts, and there were no intergroup differences in [LAC]sw during bout 3 (PP = 11.2 +/- 0.4, MP = 10.6 +/- 0.5, LP = 9.7 +/- 0.2 mmol/l). [LAC]sw was inversely related to sweating rate. Lactate excretion rate per gland was greater with the increase in PM (PP = 61.0 +/- 8.2, MP = 79.1 +/- 11.3, LP = 99.9 +/- 11.0 pmol/min; P = 0.08).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Aldosterone and prolactin response to exercise in the heat in circumpubertal boys.

Thermoregulatory responses to exercise in the heat, especially sweating pattern, differ between children and adults. To determine whether such differences may be related to hormonal responses and to assess the possible association between this response and physical maturation, three groups of circumpubertal boys cycled at 50% of maximal O2 uptake (three 20-min bouts with 10 min of rest between bouts) in 42 degrees C at 20% relative humidity. On the basis of Tanner staging, 11 were prepubertal (PP), 12 midpubertal (MP), and 7 late pubertal (LP). Water ingestion was encouraged to minimize dehydration. Venous blood was sampled before and immediately after the session. Changes in heart rate, rectal temperature, and percent decrease in plasma volume did not differ among groups. There was no change in plasma osmolality in any of the groups. Resting testosterone concentrations were higher with increased level of physical maturity (PP = 0.4 +/- 0.1, MP = 8.2 +/- 1.9, LP = 13.8 +/- 1.2 nmol/l; P less than 0.05). In all groups, both aldosterone (ALD) and prolactin (PRL) markedly increased after exercise in the heat (ALD: PP = 161 +/- 40 vs. 1,289 +/- 263, MP = 173 +/- 47 vs. 1,245 +/- 153, LP = 250 +/- 76 vs. 1,681 +/- 400 pmol/l; PRL: PP = 8.1 +/- 1.2 vs. 24.9 +/- 4.2, MP = 8.8 +/- 1.0 vs. 22.0 +/- 8.9, LP = 8.4 +/- 0.8 vs. 39.0 +/- 3.6 micrograms/l; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

The effect of prolonged intermittent exercise, combined with food deprivation, on plasma metabolite concentration.

To examine the effect of continuous fasting combined with prolonged, intermittent exercise on glucose homeostasis, 16 endurance-trained subjects, ranging in age from 18-21 years, were completely deprived of food during 81 h of field maneuvers. Water was supplied to avoid dehydration. Participants marched 10 h each night at an estimated intensity of 35-45% of mean VO2 max covering a total distance of 105 km, and had a relative rest during day time. Blood was sampled prior to the beginning of the march, at the end of 81 h, and after 24 h of recovery. Samples were analyzed for plasma glucose, insulin, alanine, free fatty acids (FFA), and 3-hydroxybutyrate (3-HB). Body weight decreased from a mean (+/- S.E.M.) of 73.0 +/- 0.6 kg at pre-march to 66.5 +/- 0.6 kg at 81 h of fasting (p less than 0.05), and remained unchanged at 24 h after march termination. Glucose, insulin, and alanine decreased, whereas FFA and 3-HB increased significantly at 81 h fast (p less than 0.05). Within 24 h of recovery all parameters changed significantly (p less than 0.05), approaching baseline values. The results indicate that in trained individuals under extreme survival conditions, as in the present study, blood glucose is maintained above hypoglycemic levels at the expense of fat and fat-derived substrates that become the main energy sources utilized.

Adult↗
PubMed1978

High density lipoproteins--correlation with cardiovascular disease in hemodialysis patients.

1) HDL levels are low in hemodialysis patients. 2) Lipid abnormalities do not correlate with the presence of CVD in hemodialysis patients. 3) Smoking may not effect blood lipid levels in hemodialysis patients. 4) Nandrolone decanoate may not play a role in CVD in hemodialysis patients. 5) Longer time on hemodialysis does not result in a decrease in triglyceride or increase in HDL levels.

Adult↗
PubMed1977

Effect of hemoperfusion of clearance of gentamicin, cephalothin, and clindamycon from plasma of normal dogs.

Nine normal dogs were divided into three groups of three. Group 1 was given an overdose of gentamicin; group 2, cephalothin; and group 3, clindamycin. Group 1 had hemoperfusion with Amberlite XE-336, and groups 2 and 3 with Amberlite XAD-4 resin adsorbents, for 6 hr with a blood flow rate of 300 ml/min. The plasma clearance and removal rates of antibiotics by the hemoperfusion columns were high. The clearance rate of gentamicin from plasma (mean +/- standard deviation) ranged from 59 +/- 30 to 199 +/- 6 ml/min, of cephalothin from 66 +/- 14 to 157 +/- 8 ml/min, and of clindamycin from 55 +/- 9 to 125 +/- 16 ml/min. Of the total dose of antibiotic administered, the hemoperfusion columns removed 67% from theplasma in group 1, 41% in group 2, and 18% in group 3. The fact that antibiotics may be rapidly removed from the blood during hemoperfusion should be considered in calculation of the therapeutic dose of antibiotic required for patients who receive this preocedure. Also, hemoperfusion can effectively and rapidly remove certain antibiotics from the blood of patients who have had a potentially toxic overdose.

Animals↗
PubMed1976

[A clinical method of testing the humidifying capicity of the human nose (author's transl)].

At the beginning attention is drawn to the fact that there is a lack of suitable clinical tests for the measurement of the humidifying and warming capacity of the nose. The great number of testing methods which have been published so far, have been either too complicated to be applied in routine checks or they were too physically strenous, so that this could not be reasonably demanded of the patients. With the help of the clinical method of testing introduced by us one can find out about norm data for the quantitiy of water needed for humidifying the inspired air in healthy persons, as well as examine the influence of pharmacons on the secretion capacity of the nose. In addition to this, pathological states such as atrophic rhinitis, vasomotoric and allergic rhinitis, patients operated with a partial maxillectomy or with total laryngectomy can also be tested as far as the humidifying and warming capacity of the nose ist concerned. In our testing method extremely dry air streams out of a compressed air cylinder with a flow of 8 1/min through a small silicone catheter at the choanal end of one nasal part and is sucked out of the other nostril with a suction flow of 5 1/min, the air passing through a psychrometer modified by us. The excess flow of 3 1/min streams from the naso- into the oropharynx most effectively preventing the air which is to be measured from mixing with the expiratory air saturated with water-vapor. A gas analyzer sensitive to carbon dioxide measures the error possible in this open system which amounts to only one percent of an average mixture with expiratory air. With the help of a psychrometer-normogramme the absolute humidity is determined from the data of the wet and both the dry thermometers. We were testing 22 healthy persons, average age 34, the norm data were established. The result is that for the hole 10 minute measurement period one nasal part needs 1.58 g water for the humidifying of the inspired air. From this it can be calculated that 456 g of water are necessary for humidifying the inspired air through both nasal parts during 24 hours. Compared with other exact methods, which, however, are not suitable for clinical tests (Ingelstedt et al.) our simple and easily workable method correlate very well.

Adult↗