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Biomedical subjects

G P Rodriguez

Publications and source records attributed to G P Rodriguez.

At least 19 recordsLinked to original sources
PubMed2001

Urinary collagen metabolite excretion in amyotrophic lateral sclerosis.

Collagen abnormalities of the spinal cord and the skin have been reported in patients with amyotrophic lateral sclerosis (ALS). The urinary concentrations of the hydroxylysine glycosides, i.e., glucosylgalactosyl hydroxylysine (glu-gal Hyl) and galactosyl hydroxylysine (gal Hyl), indicate the tissue origin of the collagen metabolites and the rate of the degradation of collagen. We measured the urinary levels of glu-gal Hyl and gal Hyl in 12 ALS patients, 10 diseased control subjects with other neurologic or muscular diseases (Control Group A), and 10 healthy control subjects (Control Group B). The urinary level of glu-gal Hyl in ALS patients was significantly lower than in the two control groups. In addition, a significant negative relationship between glu-gal Hyl urinary level and duration of illness was found in ALS patients. There was no marked difference in the urinary level of gal Hyl between ALS patients and the control groups. Our data suggest that the decreased urinary level of glu-gal Hyl may be useful in assessing the alteration in collagen metabolism in ALS and may have a relationship with the progression of ALS.

Aged↗
PubMed1999

Adaptive hepatic changes in mild stenosis of the common bile duct in the rat.

Adaptive hepatic changes were investigated in rats with mild stenosis of the common bile duct and in sham-operated controls. The studies were performed 24 h and 7-12 days postoperatively. A continuous intravenous infusion of taurocholic acid at stepwise-increasing rates was performed to explore the responses to bile acid effects. During the infusion, bile flow and the outputs of bile acids, phospholipids, cholesterol, alkaline phosphatase and gamma glutamyl transpeptidase were studied. At the end of the infusion, hepatic morphometric measurements were performed. In other experimental sets, biliary excretions of horseradish peroxidase, a marker of microtubule-dependent vesicular transport in the hepatocyte, and sulphobromophthalein, a well-known organic anion model, were studied. In other rats, bile acid pool size and composition were determined by depletion of bile. The results in rats with mild stenosis maintained for 24 h showed a greater susceptibility to the toxicity of taurocholic acid, as revealed by the abrupt decrement in bile flow at high rates of infusion, and increased outputs of phospholipids and canalicular enzymes. Conversely, rats with mild stenosis maintained for 7-12 days showed decreased bile acid maximum secretory rate and biliary outputs of phospholipids and canalicular enzymes, as well as hepatocyte hypertrophy. These findings may explain the limited hepatic and systemic repercussion of experimental mild stenosis of the common bile duct and help us to understand the early stages of constriction of the common bile duct in man.

Adaptation, Physiological↗
PubMed1996

Improved rapid method for the isolation, purification and identification of collagen glycosides.

An updated method for obtaining purified glucosylgalactosyl hydroxylysine (Glc-Gal-Hyl) is presented. Marine sponge is subjected to alkaline hydrolysis followed by ion-exchange chromatography and gel filtration. Identification is confirmed by consecutive mild acid hydrolysis of the extract to produce galactosyl hydroxylysine (Gal-Hyl) and hydroxylysine (Hyl). High-performance liquid chromatography (HPCL) with a sodium acetate-acetonitrile buffer and dabsyl chloride as the derivatizing agent demonstrated the purity of the extract and its hydrolyzates. Glc-Gal-Hyl is not commercially available but this easy and efficient method can provide large amounts of it for collagen metabolism studies.

Animals↗
PubMed1994

Prospective study of pressure ulcer risk in spinal cord injury patients.

Sixty men with spinal cord injury who had developed pressure ulcers in the past but whose skin was intact when they joined the study were followed for 2 years, or until a pressure ulcer developed. Forty of the men were contacted every 4-6 weeks to answer questions about their skin care practices and to provide a 24 hour urine sample. The others were only contacted at the beginning and the end of the study to answer a questionnaire and to provide a urine sample. Changes in skin collagen metabolism were monitored by measuring urinary excretion of a metabolite, glucosyl-galactosyl hydroxylysine (glu-gal Hyl), corrected for creatinine excretion. Sustained increases in levels of glu-gal Hyl excretion were detected at least 2 months and as much as 5 months in advance of overt clinical signs of ulcer development. Increased excretion of glu-gal Hyl was significantly associated (p < 0.05) with the development of a pressure ulcer. An increase in the urinary excretion of glu-gal Hyl is an indication of increased degradation of skin collagen. Body mass index (weight/height2) of 33% of subjects with pressure ulcers, and 12% of those without, was at least one standard deviation below the mean of all subjects. Thirty-six percent of those who smoked developed ulcers, while only 26% of the nonsmokers did.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Measurement of communicative intentions in normally developing children during structured and unstructured contexts.

The purpose of this study was to examine the effect of sampling context on measurements of communicative intentions expressed by 15 normally developing children during the prelinguistic, one-word, and multiword stages. A communication sample using both structured and unstructured contexts was collected from each subject as he or she interacted with a clinician and parent at each language stage. Direct comparisons were made between the uses of requests and comments during the structured and unstructured sampling contexts. The results indicated that the mean number of requests and comments increased significantly from the prelinguistic to the multiword stage in both contexts. Significantly more requests were used during the structured context, but no significant difference was found between the numbers of comments used in the two contexts. Factors to consider in sampling communication from developmentally young children are discussed.

Child↗
PubMed1991

Influence of outer ear resonant frequency on patterns of temporary threshold shift.

Noise-induced hearing loss following a broadband noise exposure has been characterized by a notch in the audiogram in the 3.0 to 6.0 kHz range. It has been postulated that loss of sensitivity in this frequency range is related to the primary resonant frequency of the external auditory meatus. In order to further explore this hypothesis, 31 normal-hearing subjects provided measurements of acoustic gain of the external ear and temporary threshold shift (TTS). Subjects completed sweep frequency Bekesy tracking procedures prior to and immediately following a 30-minute broadband noise exposure (95 dBA). The frequency maximally affected by the noise exposure (Max TTS) was correlated to primary resonant frequency of the outer ear (Max RF). A significant positive correlation between these two measures was identified. A 100 Hz difference in Max RF resulted in approximately a 140 Hz change in Max TTS. Thus, the external ear plays a significant role in the frequencies affected by a broadband noise exposure.

Acoustics↗
PubMed1990

Central auditory processing in normal-hearing elderly adults.

Central auditory and linguistic functions were assessed in a group of 25 essentially normal-hearing, cognitively intact elderly adults. Inclusion in the study required normal performance on the Mini-Mental State Examination Procedures used to evaluate central auditory performance included monosyllabic word lists, the Synthetic Sentence Identification-Ipsilateral Competing Message (SSI-ICM) test, the Dichotic Digits test and the Staggered Spondaic Word test. Linguistic competence was assessed utilizing subtests of the Boston Diagnostic Aphasia test and the Revised Token test. Results indicate that central auditory involvement can occur without a concomitant decline in peripheral hearing sensitivity, cognitive function, or linguistic competence. Our findings also suggest, that for the type of individuals included in this study, the SSI-ICM appears to be the most sensitive measure to changes in central auditory processing abilities with advancing age.

Aged↗
PubMed1989

Collagen metabolite excretion as a predictor of bone- and skin-related complications in spinal cord injury.

Immediately after the trauma, spinal cord injury patients have an increased rate of collagen synthesis and an even greater increase of collagen degradation. Collagen lost from bone is implicated in the etiology of osteoporosis and heterotopic ossification, and collagen lost from skin might lead to a propensity to develop pressure ulcers. The urinary excretion of two collagen metabolites has been monitored and their fluctuation related to the onset of skin or bone complications in these patients. One metabolite, glucosyl-galactosyl hydroxylysine, is more abundant in skin collagen; the other, galactosyl hydroxylysine, is more abundant in bone collagen. The excretion of both metabolites increases after injury, reaching a peak between three and six months after injury, and declines gradually, reaching control values about a year after injury. If a skin pressure ulcer develops, the urinary excretion of the diglycoside remains elevated instead of gradually decreasing. Similarly, if osteoporosis or heterotopic ossification is diagnosed, the monoglycoside excretion does not return to control values until the bone turnover stabilizes. Monitoring of the urinary excretion of both glycosides might prove helpful in prompting early examination to establish the presence of emerging skin and bone complications. Thus, aggressive preventive therapy could be given sooner.

Adolescent↗
PubMed1989

Phenomenologic aspects of the acoustic reflex following noise exposure.

Thirty-seven normal hearing subjects were exposed to broadband noise for 2 hours at 90 dB (Lp). Measures of behavioral thresholds and acoustic reflex activity were completed prior to and following the noise exposure. As expected, temporary threshold shift was obtained at several different frequencies (1.0-6.0 kHz). In addition, reflex threshold shift occurred for all pure-tone elicitors under evaluation (0.5 to 4.0 kHz). The observed shift in acoustic reflex threshold at 0.5 kHz without a concomitant change in behavioral sensitivity reveals the limitation of utilizing behavioral threshold testing as the sole measure of cochlear disruption. Changes in acoustic reflex onset latency and magnitude were not observed after compensating for shifts in acoustic reflex threshold.

Acoustic Stimulation↗
PubMed1988

Biochemical changes in skin composition in spinal cord injury: a possible contribution to decubitus ulcers.

Patients with spinal cord injury (SCI) have an increased susceptibility to ulcers of the skin due to pressure. Immediately after the injury, SCI patients have a greatly increased degradation of collagen from both bone and skin. Loss of collagen from the skin could account for a reduction of the skin's ability to resist mechanical insults. This paper describes the results of an investigation into the role of collagen metabolism in the etiology of pressure ulcers. Skin biopsies have been obtained from healthy non-paralysed volunteers, and from insensitive and sensitive skin in SCI patients. The amino acid content of the insensitive skin was considerably lower than in sensitive skin. The activity of the enzyme lysyl hydroxylase was also lower in the insensitive skin. Lysyl hydroxylase activity in the sensitive skin was similar to enzyme activity in control skin biopsies of the same body area.

Amino Acids↗
PubMed1988

Adaptation properties of the acoustic reflex in response to continuous-, intermittent- and industrial-noise stimulation.

Adaptation properties of the acoustic reflex (AR) were evaluated in a group of normal-hearing subjects. Signals used to elicit the AR included: (1) continuous broad-band noise; (2) broad-band noise interrupted every 7.5 s. with pauses of 250, 500 and 750 ms, and (3) industrial noise. AR activity was continuously monitored for a period of 5 min. Values of acoustic admittance at the beginning and end of the test period were used to calculate percent adaptation for all five elicitor conditions. The greatest adaptation occurred during continuous broad-band-noise stimulation and the least adaptation was observed under the industrial-noise condition. The AR system appears to be resistant to the process of adaptation when activated by stimuli with periodically changing temporal signatures. Results also support previous investigations that demonstrate that the AR is extremely active in certain industrial environments.

Acoustic Stimulation↗
PubMed1987

Ear canal volume and variability in the patterns of temporary threshold shifts.

Ear canal resonance is thought to be responsible for the prominent loss of hearing in the 3.0 to 6.0 kHz region caused by over-exposure to noise. Relationships were identified between frequency-of-maximum temporary threshold shift (TTS) and physical measurements of the ear canal in 56 subjects. TTSs were produced by two separate exposures to broadband noise of either 2 hr or 20 minute duration. Ear canal volume was estimated from admittance tympanograms, diameter of the canal opening was measured, and canal length was calculated. Thirty subjects suffered the greatest TTS at 4.0 kHz, while 17 and 9 subjects had the greatest shift at 3.0 and 6.0 kHz, respectively. With subjects grouped according to frequency-of-maximum TTS, mean ear canal volume was found to be significantly different. Subjects with larger volumes were more likely to suffer the greatest loss at 3.0 kHz. Accordingly, subjects with smaller ear canal volumes suffered peak hearing loss at 6.0 kHz. Significant correlations were identified between ear canal volume and calculated length (resonance). Also, modest correlations were noted between frequency-of-maximum TTS and volume as well as TTS and length.

Acoustic Stimulation↗
PubMed1986

Adrenergic receptors in insensitive skin of spinal cord injured patients.

The factors responsible for the increased susceptibility to decubitus ulcers of the insensitive skin of spinal cord injury (SCI) patients are not known. Autonomic dysfunction leading to defective vascularity is a possibility. SCI removes cerebral control of the isolated nervous system which may mimic denervation hypersensitivity of autonomic neural synapses, where an increase in number and a scattering of the receptors on the postsynaptic membrane leads to abnormal responses. Since adrenergic receptors mediate vascular tone and regulate blood flow in the skin, it would be of great interest to determine whether the number and the concentration of receptors in the insensitive skin of SCI patients is modified as a function of time since injury. To achieve this aim, alpha and beta adrenergic receptors were measured in biopsies obtained from intact skin used to surgically repair decubitus ulcers in SCI patients admitted to The Institute for Rehabilitation and Research. Receptors were identified by competitive radioligand-binding assays in whole skin homogenates. Patients were divided into two groups: patients injured less than five years ("early") and patients injured more than five years ("late"). Alpha and beta adrenergic receptors in both cervical and thoracic SCI patients decreased in density in the "late" patients. The small sample size and the inherent large errors of the assay precluded achievement of statistically significant differences. Nevertheless, a definite trend is seen: Disconnection of the adrenergic neurons from brain integration may mimic denervation and lead to abnormal vascular responses in the insensitive skin.

Adult↗
PubMed1986

Failure of weight training to affect urinary indices of protein metabolism in men.

It is commonly believed by some athletes that strength building exercise "tears down" skeletal muscle tissue, thereby enhancing the dietary need for protein, but this has not been demonstrated. Ten college-age males served as subjects in a 15-d, controlled feeding study. The men were 23.1 +/- 2.2 yr old (mean +/- SD), 177 +/- 5 cm in height, and 71.7 +/- 9.1 kg in body weight (study days = 1 to 15). The lacto-ovo-vegetarian diet provided 0.9 g/kg protein and 15.1 +/- 0.4 MJ (3,604 +/- 104 kcal) . d-1 energy (study days = 6 to 15). On days 8 and 12, subjects participated in a standardized strength building, weight training exercise regimen. Post-exercise days 9 to 11 and 13 to 15 were designated for recovery. Daily (24-h) urine collections were analyzed for ammonia, creatinine, 3-methylhistidine, total nitrogen, and urea. There was no acute (24-h) effect of weight training exercise on any excretion levels. In particular, urinary 3-methylhistidine excretion data indicate that skeletal muscle protein catabolism was not changed by isolated bouts of weight training exercise.

Adult↗
PubMed1984

Measurement of hydroxylysine glycosides in urine and its application to spinal cord injury.

A new technique to evaluate the degradation of skin or bone collagen by measuring glucosylgalactosyl hydroxylysine and galactosyl hydroxylysine is presented. The method utilizes an automated amino acid analyzer. Eluents used are lithium buffers, and the color reagent is ninhydrin. Both glycosides elute in 3.5 h. Samples require minimum preparation. Urinary concentrations of both glycosides in ten patients with cervical spinal cord injuries of less than six months duration were higher than in five healthy controls. Proportional increases were different for each of the two glycosides. Variations in the proportional increase of each glycoside indicate different rates of degradation of skin and bone collagen. Repeated evaluations of the two urinary glycosides may help to predict whether patients are likely to develop skin- or bone-related clinical complications.

Adult↗
PubMed1982

Spinal cord injury hypercalcemia: therapeutic profile.

During the course of hospitalization for comprehensive rehabilitation, a 14-year-old boy with C4 spinal cord injury and hypercalcemia was treated with 5 different treatment regimens which were instituted to reduce the hypercalcemia and associated complications. These regimens included low calcium diet, steroids, oral phosphates, intravenous saline, diuretics, hyperalimentation, calcitonin and spironolactone in various combinations, and mobilization. Careful metabolic monitoring carried out throughout hospitalization permitted the evaluation in retrospect of the impact of each treatment regimen, and, to a lesser extent, the impact of their individual components. Among all the therapeutic modalities, the most effective variables in reducing hypercalcemia in this patient were mobilization in the form of wheelchair sitting for long-term effects, and saline, furosemide, and calcitonin for short-term effects.

Adolescent↗
PubMed1981

Urinary in vitro sedimentation: effects of nondialyzable components and heparin.

To determine whether nondialyzable urinary solids which are rich in hydroxyproline polypeptides, could act as nuclei in the formation of crystal aggregates, urine from patients with spinal cord injury (SCI) was pooled for 7 days and its nondialyzable fraction was separated and lyophilized. The ability of this extract to influence the formation of crystals was tested in vitro in a synthetic urine system. The concentrations of calcium, hydroxyproline, and uric acid, as well as the pH, were varied to simulate a range of possible situations in vitro. In the presence of the extracts, when the pH of the synthetic urine was increased from 5.5 to 6.5, the weight of the sediment decreased; in contrast, when the pH was increased from 7.0 to 8.5, the weight of the sediment increased. A similar synthetic urine system was used to test the effect of heparin, a medication often given SCI patients, on crystallization. In this instance, the pH was not altered. Heparin lowered the weight of sediments formed in solutions with uric acid concentrations of less than 50 mg/dl, but had varying effects in solutions with higher uric acid concentrations.

Calcium↗