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Biomedical subjects

R Snow

Publications and source records attributed to R Snow.

At least 19 recordsLinked to original sources
PubMed1992

Magnetic resonance imaging of body fat of athletes compared with controls, and the oxidative metabolism of estradiol.

The extent of 2-hydroxylation of estradiol (E2), which yields a non-estrogenic metabolite (2-OHE1), increased significantly with decreasing subcutaneous fat (ScF)/total volume percent (TV%) and total fat (TF)/TV% evaluated by magnetic resonance imaging (MRI) for five athletes during low- and high-intensity training, and four controls. The increase in 2-hydroxylation with decreasing adiposity was associated with anovulation and amenorrhea among the athletes.

Adipose Tissue↗
PubMed1991

Patterns and severity of conduction abnormalities in Guillain-Barré syndrome.

Whether the conduction abnormalities and lesions underlying them are randomly distributed throughout the peripheral nervous system (PNS) or certain regions are selectively more vulnerable to attack is an unresolved question in Guillain-Barré syndrome (GBS). To examine this question, 15 cases of GBS were comprehensively examined using electrophysiological techniques which allowed close examination, quantitation and comparison of conduction abnormalities in motor and sensory fibres of the upper limb between the spinal cord and the distal extremities of the nerve fibres. Comparison of these studies with results expected in a model where the chances of conduction failure were uniformly distributed led to the conclusion that conduction slowing and block were not uniformly distributed in most cases. Conduction block was maximal in the terminal segment distal to the wrist and to a lesser extent both conduction block and conduction slowing were disproportionately greater across the elbow and in the axillary to spinal root segments in over one half of the cases. These findings support the hypothesis that certain regions, perhaps because of relative deficiencies of the blood-nerve barrier, may be more vulnerable in GBS than other regions.

Electric Stimulation↗
PubMed1991

[The impact of impregnated mosquito nets on prevalence and morbidity related to malaria in sub-Saharan africa].

Insecticide treated bed nets (permethrin, deltamethrin and lambda cyalothrin) were used for malaria control in The Gambia, Burkina Faso and Tanzania where Anopheles gambiae (and An.funestus in Burkina Faso) is the main vector. Treated mosquito nets are efficient when used on a large scale and not on an individual level. Such a large scale use, acting on longevity and infectivity of vectors, always induced a decrease of malaria transmission by more than 90%. Treated bed nets had no significant effect on the overall parasite rate, showing that malaria transmission was not stopped. But it was usually found that there was a significantly smaller number of children with parasitemia higher than a critical threshold, a sensitive parameter of malaria morbidity. Indeed, in the three situations studied, malaria morbidity (fever + high parasitemia greater than critical level in the concerned area) has generally shown a similar drop of 60%. These data demonstrate that treated bed nets are useful to reduce transmission and morbidity. Advised as a new way for reduction of nuisance, treated bed nets were always welcomed by the populations and this method may be considered as a complementary weapon in public health.

Adolescent↗
PubMed1990

Preoperative screening: value of previous tests.

OBJECTIVE: To determine the frequency of tests done in the year before elective surgery that might substitute for preoperative screening tests and to determine the frequency of test results that change from a normal value to a value likely to alter perioperative management. DESIGN: Retrospective cohort analysis of computerized laboratory data (complete blood count, sodium, potassium, and creatinine levels, prothrombin time, and partial thromboplastin time). SETTING: Urban tertiary care Veterans Affairs Hospital. PATIENTS: Consecutive sample of 1109 patients who had elective surgery in 1988. MEASUREMENTS AND MAIN RESULTS: At admission, 7549 preoperative tests were done, 47% of which duplicated tests performed in the previous year. Of 3096 previous results that were normal as defined by hospital reference range and done closest to the time of but before admission (median interval, 2 months), 13 (0.4%; 95% CI, 0.2% to 0.7%), repeat values were outside a range considered acceptable for surgery. Most of the abnormalities were predictable from the patient's history, and most were not noted in the medical record. Of 461 previous tests that were abnormal, 78 (17%; CI, 13% to 20%) repeat values at admission were outside a range considered acceptable for surgery (P less than 0.001, frequency of clinically important abnormalities of patients with normal previous results with those with abnormal previous results). CONCLUSIONS: Physicians evaluating patients preoperatively could safely substitute the previous test results analyzed in this study for preoperative screening tests if the previous tests are normal and no obvious indication for retesting is present.

Aged↗
PubMed1990

Norfloxacin use in urinary tract infection by urologists and infectious disease specialists.

One hundred thirty-one patients of urologists and infectious disease specialists were entered into an open trial of norfloxacin in the therapy of urinary tract infections (UTIs). All patients were evaluable for tolerability and 98 were evaluable for efficacy. The patient population in this study was older (mean age 53 years) and had more underlying urogenital disorders (30%) or recent invasive urologic procedures (20%) than the typical patient population with UTIs. Over 50% of the patients had infections due to organisms other than Escherichia coli, including Pseudomonas aeruginosa (14), Klebsiella pneumoniae (5), Enterobacter spp (3) and Group D streptococcus (6). Clinical and bacteriologic cure rates were 90 and 91%, respectively. Side effects occurred in 5 patients and were generally mild.

Administration, Oral↗
PubMed1990

Denervation in hemiplegic muscles.

This study examined the frequency of denervation activity in hemiplegic muscles in relation to the size and location of the central lesion. We studied 20 patients, 14 with major unilateral cerebral infarctions in the middle cerebral or internal carotid territories; four with a single lacune in the pons, internal capsule, or thalamus; and two with precentral infarcts. Using somatosensory evoked potentials, motor conduction studies, and assessments of conduction across the plexus and roots, we detected no conduction abnormalities on the affected side. Fibrillation was common in both groups, especially in distal and intermediate muscles. The distribution of the fibrillation and the normal conduction studies suggested that trauma of peripheral nerves was not a factor. Although the normal conduction studies and pattern of fibrillation activity do not exclude peripheral nerve trauma as the cause of the fibrillation, we suggest that transsynaptic degeneration is a reasonable alternative explanation.

Action Potentials↗
PubMed1989

Exercise tolerance in the heat on low and normal salt intakes.

1. Salt restriction is recommended in the treatment of hypertension and is included in national dietary guidelines, but its effect on exercise in hot conditions has not been extensively studied. 2. The effects of 2 weeks on two levels of salt intake (50 and 150 mmol/day) on the ability to exercise (60% of maximal oxygen uptake) in a hot environment (35 degrees C) were studied in eight healthy normotensive subjects. 3. All subjects were able to complete the exercise load on the two levels of salt intake. No differences in mean oxygen uptake, heart rate or rectal temperature during exercise were observed between the two salt intakes. 4. Plasma sodium, potassium and osmolality were similar on the two salt intakes both before and during exercise. Plasma renin activity and aldosterone concentration were elevated after 2 weeks on the reduced salt intake and remained so during exercise. 5. The estimated sweat rate during exercise was similar on the two salt intakes but the loss of sodium was less on the low salt intake. 6. On the basis of these results it is concluded that moderate salt restriction does not impair the ability to exercise in a hot environment.

Adult↗
PubMed1989

Confirmation by magnetic resonance imaging of Bell's cruciate paralysis in a young child with Chiari type I malformation and minor head trauma.

We report the case of a young girl who suffered bilateral upper extremity paralysis after minor head trauma. Her clinical picture, as well as radiographic evidence of a fracture at C1, led to the diagnosis of Bell's cruciate paralysis, caused by a small lesion in the rostral part of the pyramidal decussation. Magnetic resonance images showed, in addition to a Chiari Type I malformation, an abnormality in the medulla. All previous cases of cruciate paralysis lack both pathological and radiographic supporting evidence.

Arnold-Chiari Malformation↗
PubMed1988

Motor unit estimates in the biceps-brachialis in amyotrophic lateral sclerosis.

A newly developed technique for estimating the number of motor units in the biceps-brachialis muscles and for studying the innervation patterns of motor units in the same muscles has been applied to the study of 17 patients with amyotrophic lateral sclerosis (ALS). Although severe motor unit losses were seen in many ALS cases, in most there were clear indications of increases in innervation densities, linked potentials, and blocking. This technique provides a powerful new tool for quantitatively assessing the extent of motor unit losses and the accompanying changes in innervation patterns in ALS.

Adult↗
PubMed1988

Methods for estimating numbers of motor units in biceps-brachialis muscles and losses of motor units with aging.

This paper presents a new method, here applied to the biceps-brachialis muscles, for estimating motor unit numbers in healthy subjects. This method combines isometric contraction, intramuscular needle electrode recordings, and spike-triggered averaging techniques to measure the sizes of motor unit potentials as recorded in the innervation zone with surface electrodes. The number of motor units is then estimated by division of the maximum biceps-brachialis "M" potential recorded with the same surface electrodes and evoked by supramaximal stimulation of the musculocutaneous nerve, by the mean of at least 10 surface-recorded motor unit potentials. The requisite intramuscular recordings provide additional information as to innervation density, incidence of linked potentials, and impulse blocking, phenomena that are particularly common in neurogenic and myogenic disorders. There was clear evidence of losses of motor units in older subjects: subjects over 60 years of age having approximately half the numbers of motor units of subjects under 60 years of age.

Adult↗
PubMed1986

Cephalosporins in cutaneous infections. A prospective comparison of two dosage regimens of ceftazidime for therapy of skin and skin structure infections.

The safety and efficacy of ceftazidime administered as 0.5 g every 8 hours (q8h) or 1.0 g q8h for at least 5 days were compared in 197 patients and found to be effective in the treatment of cellulitis, abscesses, skin ulcers, and wound infections. Staphylococcus aureus was the predominant pathogen in both treatment groups with approximately half of the isolates from each treatment group being gram-positive. Pseudomonas aeruginosa was the most common gram-negative isolate. P. aeruginosa, Proteus mirabilis, and Escherichia coli each comprised 5-12% of the isolates from each treatment group. Clinical cure or improvement was achieved in 98.7% of the patients in each treatment group. Concurrently with clinically successful treatment, a high rate of bacteriologic eradication without superinfection was achieved with the 0.5-g regimen (84% of all isolates) and the 1.0-g regimen (92%).

Adolescent↗
PubMed1985

Adaptation of saccadic and vestibulo-ocular systems after extraocular muscle tenectomy.

Adaptation of saccadic magnitude and vestibulo-ocular reflex gain (VOR) was examined in six monkeys that had undergone a tenectomy of the medial and lateral recti of one eye. After the tenectomy, when the normal eye was patched, a conjugate increase in saccadic magnitude and VOR was observed in both eyes. Subsequent unpatching resulted in selective (nonconjugate) changes in the two eyes such that control values of saccadic magnitude and VOR gain were eventually reestablished in both eyes. Evidence that this return to normal was mediated by a selective adaptation of the neural innervation to one eye was provided by the following observations: (1) saccades in the normal eye were of a lower peak velocity and longer duration after normalization than prior to the tenectomy; and (2) repatching the tenectomized eye after normalization produced a selective return of deficits in that eye over a period of a few days. Thus, the saccadic and vestibulo-ocular systems can be adapted in both a conjugate and a selective or nonconjugate fashion.

Animals↗
PubMed1972

Emergency medical transportation. A survey of California ambulance operations.

The most urgent recommendation expressed by physicians, Red Cross officials, ambulance operators and others polled in this ambulance survey was to make much more emergency medical care training available to ambulance personnel. Very few sick and injured receive first aid before an ambulance arrives. Therefore there is also an urgent need to train and motivate the public to provide first aid at the scene of the emergency. Urban ambulances usually respond within 10 minutes, but often rural ambulances take more than 30 minutes to reach an emergency. It is during this interim that lives which could be saved by prompt first aid are lost. Little use has been made of aircraft as emergency ambulances; in 1968, only one emergency trip in 1500 was made by helicopter. Also, California has fewer ambulances which make fewer emergency trips on a population basis than the country at large. Communications at all levels need attention. Seventy-eight percent of the ambulance operations serving the public are not listed among the emergency numbers on the inside front page of telephone directories. Less than ten percent of ambulances have direct radio communication with hospitals. In California most ambulance services are commercially operated and there are formidable financial problems which must be solved before these services can be brought into place as a part of the emergency medical care system.

Accidents, Traffic↗
PubMedDate not supplied

The chromosomal constitution of wine strains of Saccharomyces cerevisiae.

A general procedure is described for determining the chromosomal constitution of industrial strains of Saccharomyces cerevisiae based on analysis of segregation frequencies for input markers among random spore progeny of industrial-laboratory strain hybrids. The multiply auxotrophic haploid testers used carried a dominant erythromycin-resistance marker, allowing hybrids to be selected in mass matings with spores produced by the wild-type industrial strains. Analysis of a number of independent crosses between the haploid testers and an unselected population of spores of each wine strain distinguished between disomic, trisomic and tetrasomic chromosomal complements in the parents. Possible explanations for a significant class of aberrant segregation frequencies are discussed. Results of the analysis indicate that UCD Enology 522 (Montrachet) is diploid and possibly trisomic for chromosome VII; 522X is diploid; UCD Enology 505 (California Champagne) is disomic for chromosome XVI, trisomic for chromosomes I, II, III, VI, VIII, IX, X, XII, XV, tetrasomic for chromosomes IV, XI, XIII, XIV and either trisomic or tetrasomic for chromosomes V and VII; and that UCD Enology 595 (Pasteur Champagne) is disomic for chromosomes I, II, III, IX, XVI, trisomic for chromosomes IV, VI, X, XII, XIV, XV, tetrasomic for chromosomes V, VIII, XI, XIII and either disomic or tetrasomic for chromosome VII.

Chromosomes, Fungal↗