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Biomedical subjects

L A Christensen

Publications and source records attributed to L A Christensen.

At least 19 recordsLinked to original sources
PubMed1999

Aspects of motivation of a volunteer AIDS care team program.

The South Carolina AIDS Care Team Program, directed by The Ecumenical AIDS Ministry, a component of the South Carolina Christian Action Council, provides emotional and supportive services to people living with HIV and AIDS. A sample of volunteer care team members participated in five focus groups as part of a process evaluation. Care teams were asked to participate based on years since training (new vs. experienced), race (white vs. African American), and location (urban vs. rural). Volunteers were motivated to become involved in a care team through previous contact with a person with AIDS, a general sense of altruism, and influences from their faith community. Due to the emotionally demanding nature of the work, motivation to remain a volunteer was also examined. It was discovered that a support system, the expression of faith, support of their faith community, and coping with the death of a care partner were essential elements for sustaining care team involvement. The implications of this study are useful to volunteer programs through faith communities to meet the growing need of people living with HIV and AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Antiviral therapy in a child with pediatric human immunodeficiency virus (HIV): case study of audiologic findings.

Over the past decade, much research has been conducted to determine the auditory consequences of human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS). This research, primarily using adult patients, has focused on the involvement of the central auditory nervous system (CANS). Measures of auditory evoked potentials, particularly the auditory brainstem response (ABR), can document changes in the CANS as the disease progresses and during treatment with antiviral therapies such as zidovudine (AZT) and didanosine (ddI). This case study presents the audiologic findings for a child with HIV infection. Evaluations were performed over a 2-year period prior to the initiation of antiviral therapy and following treatment. Audiologic measures included behavioral audiometry, tympanometry, otoacoustic emissions, and ABR latency/intensity functions and rate studies. Findings indicated a gradual shortening of all ABR component latencies following the initiation of antiviral therapy. In addition, a high-frequency hearing loss was detected during the final evaluation subsequent to 19 months of treatment with AZT and ddI.

Anti-HIV Agents↗
PubMed1997

A comparison of the benefit provided by well-fit linear hearing aids and instruments with automatic reductions of low-frequency gain.

In this clinical study, 110 patients seen at three different clinical facilities were fit binaurally with linear, in-the-canal (ITC) hearing aids. All patients were new hearing aid users. Each of the hearing aids was equipped with an adjustable control that could be set by one of the audiologists (Audiologist A) at each site to convert it from a linear instrument to an experimental nonlinear one with automatic reduction of low-frquency gain at high input levels (or base increase at low levels, BILL). Both the patient and the audiologist performing the outcome testing at each site (Audiologist B) were blind as to the present setting of the hearing aid. Each participant was enrolled in the study for a total of 12 weeks, with the hearing aid set to either the linear or BILL-processing mode of operation for the first 8 weeks and the opposite setting for a subsequent 4-week period. In summary, this was a prospective, doubleblind, crossover study of 110 new hearing aid users. Outcome measures focused on hearing-aid benefit and included both objective and subjective measures. Objective measures were derived from scores on the Northwestern University Auditory Test NO. 6 (NU-6) and the Connected Speech Test (CST) obtained for all possible combinations of two speech presentation levels (60 and 75 dB SPL) two types of background noise (cafeteria noise and multitalker babble), and two signal-to-noise ratios (+5 and +10 dB). Subjective outcome measures included magnitude estimation of listening effort (MELE), the abbreviated form of the Hearing Aid Performance Inventory (HAPI), and estimations of hearing-aid usage based on daily-use logs kept by the participants. All of these measures were used to evaluate the benefit provided by linear amplification and the benefit resulting from the experimental BILL processing. Participant preferences for the experimental BILL-processing scheme or linear processing were also examined by using a paired-comparison task at the end of the study. Results were analyzed separately for three subgroups of patients (mild, moderate, severe) formed on the basis of their average hearing loss at 500, 1000, 2000, and 4000 Hz. In all three subgroups, significant improvement in performance was observed for linear amplification and for BILL processing when compared to unaided performance. There were no significant differences in aided performance, however, between linear processing and the experimental BILL processing.

Aged↗
PubMed1997

Identification of multidimensional stimuli containing speech cues and the effects of training.

The purpose of this study was to determine how listeners with normal hearing make use of cues from multiple, independent stimulus dimensions when classifying synthesized stimuli containing acoustic cues found in speech. Listeners classified synthesized stimuli that differed on three independent and discriminable dimensions. The three dimensions of the stimuli included: (1) the fricative spectrum center frequency; (2) the slope of the frequency transition; and (3) the duration of the temporal gap. Each of the three dimensions could take on one of three possible values. Twenty-seven stimuli were synthesized using all possible combinations of the values on the three dimensions. Multidimensional scaling of paired-comparison similarity judgments confirmed the existence of three perceptual dimensions. Listeners were then trained to classify three exemplar stimuli as "circle," "triangle," and "square," respectively. Following this training, subjects classified all 27 stimuli as "circle," "triangle," and "square." From this it was determined how each listener's attention was distributed among the dimensions. Results indicated the listeners did not pay equal attention to the three stimulus dimensions. In addition, it was demonstrated that it was possible to train a listener to attend to a dimension that was not previously used to classify the stimuli.

Adult↗
PubMed1996

Identification of multidimensional complex sounds having parallel dimension structure.

The present series of experiments examined the ability of normal-hearing listeners to make use of cues from multiple, independent stimulus dimensions when classifying multidimensional complex sounds. Ten listeners classified complex sound pulses that differed along three independent dimensions. The stimuli were 100 ms in duration and were synthesized using five simultaneous sinusoids. The three dimensions of the complex stimuli manipulated in this experiment were harmonicity, spectral shape, and amplitude envelope. Each stimulus dimension could take on one of two values, referred to here as target or nontarget. Eight stimuli were synthesized using all possible combinations of the dimension values. Subjects were trained to label two stimuli, the two having either all-target or all-nontarget values, as "+" and "0," respectively. Following this training, subjects were asked to classify all eight stimuli as either "+" or "0." Results of this experiment indicated that listeners preferred to classify these stimuli on the basis of one stimulus dimension. However, the preferred dimension was not the same for all of the listeners. In addition, it was demonstrated that it was possible to train an individual to use a dimension other than the one or two initially preferred when classifying the stimuli.

Auditory Perception↗
PubMed1996

Influence of anesthetics on the peripheral blood microfilaremia of Brugia malayi in the Mongolian jird, Meriones unguiculatus.

The effects of anesthetics on the peripheral blood microfilaremia of Brugia malayi in Meriones unguiculatus were investigated. Microfilaremias were assessed by orbital puncture prior to and following the use, either individually or in tandem, of ether, Rompun, Ketaset, and sodium pentobarbital. Results indicate that the peripheral microfilaremia varied dramatically, depending on the anesthetic administered. Although microfilaremias were not affected by an initial ether exposure, counts of microfilariae increased significantly when jirds received Rompun and Ketaset, or Ketaset alone. Administration of sodium pentobarbital did not increase the number of microfilariae observed in the peripheral blood. The mode of action differs between these drugs and is likely responsible for the different effects observed. Consequently, studies involving vector-parasite interactions should take precautions to prevent parasite-induced vector mortality due to the ingestion of large numbers of microfilariae induced in the peripheral bloodstream by certain anesthetics.

Analysis of Variance↗
PubMed1994

Factors associated with individual differences in clinical measures of speech recognition among the elderly.

In the present study, the speech-recognition performance of 50 subjects aged 63 to 83 years was measured for a wide range of materials (nonsense syllables, monosyllabic words, sentences) and listening conditions (presentation levels of 70 and 90 dB SPL, both in quiet and in a noise background). In addition to complete audiologic evaluations, measures of auditory processing (the Test of Basic Auditory Capabilities [TBAC], Watson, 1987) and cognitive function (Wechsler Adult Intelligence Scale-Revised [WAIS-R], and the Wechsler Memory Scale-Revised [WMS-R], Wechsler, 1981, 1987) were obtained from all subjects. Principal component analyses were applied to each of the three sets of measures (speech-recognition, auditory, and cognitive) prior to examining associations among the sets using canonical analyses. Two principal components captured most of the systematic variation in performance sampled by the set of 20 speech-recognition measures. Hearing loss emerged as the single largest factor associated with individual differences in speech-recognition performance among the elderly, accounting for 70-75% of the total variance in speech-recognition performance, with the measures of auditory processing and cognitive function accounting for little or no additional variance.

Acoustic Stimulation↗
PubMed1994

Comparative bioavailability of 5-aminosalicylic acid from a controlled release preparation and an azo-bond preparation.

BACKGROUND: Knowledge of the bioavailability of 5-aminosalicylic acid (5-ASA, mesalazine) from the different 5-ASA-containing drugs is important for rational therapy of inflammatory bowel diseases. METHODS: The local and systemic bioavailability of 5-ASA from a controlled release 5-ASA preparation (Pentasa--2, 4 or 6 g/day) was investigated and compared with the azo-bond 5-ASA preparation olsalazine (Dipentum--2 g/day) in 13 healthy volunteers during steady state conditions. RESULTS: The therapeutically relevant parameter of 5-ASA at the rectal level, expressed as the mean concentration in faecal water, showed a significant trend towards higher concentrations with increasing Pentasa dose: 9.2 mmol/L, 19.0 mmol/L and 24.4 mmol/L, respectively. The concentration of olsalazine 2 g/day was 16.0 mmol/L. The concentration of the metabolite N-acetyl-5-aminosalicylic acid (Ac-5-ASA) did not rise with increasing Pentasa dose, indicating saturable presystemic acetylating capacity of 5-ASA. Total urinary excretion of 5-ASA and Ac-5-ASA, as a percentage of the daily ingested 5-ASA dose, remained constant on the three Pentasa doses, but there was a significant increase in the 5-ASA fraction. Mean steady state plasma concentrations of 5-ASA and Ac-5-ASA were significantly higher on Pentasa 4 g/day and 6 g/day than on 2 g/day. Values on Pentasa 2 g/day were comparable with those on olsalazine 2 g/day. CONCLUSIONS: The study confirmed that 5-ASA is released from Pentasa in a predictable manner, the amount released increasing with dose. Olsalazine is an excellent generator of 5-ASA in the colon.

Administration, Oral↗
PubMed1994

Disposition of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid in fetal and maternal body fluids during treatment with different 5-aminosalicylic acid preparations.

STUDY OBJECTIVE: To determine the concentration of 5-aminosalicylic acid (5-ASA) and the metabolite N-acetyl-5-aminosalicylic acid (Ac-5-ASA) in the maternal and fetal plasma at delivery and in the maternal milk post partum. DESIGN AND STUDY SUBJECTS: Pregnant and lactating women with chronic inflammatory bowel disease, treated with different pure 5-ASA preparations participated in the study. At delivery, samples of fetal and maternal plasma were obtained from nine women. The excretion in milk was measured and the time of medicine intake was registered during a 24 h period 2-4 weeks after delivery in 13 women. RESULTS: Concentrations of 5-ASA in the fetal plasma were lower than in maternal plasma. Plasma concentrations of Ac-5-ASA were detectable in all the nine samples and similar levels in the mother and the fetus were found at the time of delivery. In three women 5-ASA was detected in the milk in low concentrations. The concentration of Ac-5-ASA in the milk varied considerably during the 24 h collection period, and also between individuals; its concentration tended to be higher than in the plasma. No time relation between medicine intake and maximal concentration in the milk was found. Based on the maximal Ac-5-ASA concentration and a milk intake of one liter/daily, the newborn receives less than 15 mg Ac-5-ASA daily. CONCLUSION: The study indicates that treatment with pure 5-ASA preparations in conventional doses is without risk to the fetus and the newborn.

Aminosalicylic Acids↗
PubMed1994

Effect of olsalazine and mesalazine on intraluminal pH of the duodenum and proximal jejunum in healthy humans.

BACKGROUND: Treatment of inflammatory bowel disease with olsalazine causes diarrhoea in 10% of patients. This is claimed to be caused by a drug effect on mucosal transport in the small intestine, which might be reflected in the intraluminal pH. We aimed to study the effect on jejunal pH of olsalazine (Dipentum) and an alternative preparation, slow-release mesalazine (Pentasa). METHODS: Thirteen healthy volunteers, seven male and six female, participated in a randomized, crossover study. Steady-state conditions were obtained after ingestion of 2 g or 6 g mesalazine daily or 2 g olsalazine daily for 1 week. The pH of the duodenum and proximal jejunum was measured by using pH-sensitive, radiotransmitting capsules, the location of which was confirmed by fluoroscopy. RESULTS: No effect of either drug on duodenal pH was detected. Mean duodenal pH ranged from 6.18 to 6.22. The mean pH of the pre-medication proximal jejunum was 6.02. Mesalazine had no significant effect, but olsalazine significantly increased the pH of the proximal jejunum (mean pH, 6.47). CONCLUSIONS: Our results indicate that the effect of olsalazine on jejunal transport of electrolytes and water, observed in experimental studies, also applies to human subjects in steady-state conditions, and adaptation does not occur within 6 days.

Adolescent↗
PubMed1993

Identification of oxidation products of 5-aminosalicylic acid in faeces and the study of their formation in vitro.

The formation of three oxidant-derived products of 5-aminosalicylic acid (5-ASA) in vivo was demonstrated in patients with active ulcerative colitis as well as in healthy subjects. The products were isolated from faeces by preparative HPLC and their chemical structures were found to be oxidation products of 5-ASA using 1H-NMR spectroscopy and mass spectrometry. Reactions carried out in vitro between 5-ASA and oxidants suggested to be present in the inflamed bowel verified that the hypochlorite-mediated oxidation of 5-ASA as well as the haemoglobin-catalysed H2O2-dependent oxidation of 5-ASA resulted in the formation of a single oxidation product of 5-ASA. This product was similar to, but not identical to any of the products identified in faeces from patients receiving 5-ASA. Oxygen radical-mediated oxidation of 5-ASA gave several products, different from the products isolated. Finally, it was verified that the products formed in vivo are not formed as a result of autooxidation of 5-ASA either in faeces extract or in pharmaceuticals.

Aminosalicylic Acids↗
PubMed1993

Bioavailability of 5-aminosalicyclic acid from slow release 5-aminosalicyclic acid drug and sulfasalazine in normal children.

The bioavailability of a controlled release 5-aminosalicyclic acid preparation (Pentasa) was investigated in nine healthy children after a medication period of six days (1000 mg/day) and compared with sulfasalazine (Salazopyrin) (2000 mg/day). The local bioavailability in the distal gut lumen, reflected by the 5-aminosalicylic acid concentration in the fecal water, showed comparable values after Pentasa (4.44 mmol/liter) and Salazopyrin (6.25 mmol/liter). The concentration of N-acetyl-5-ASA was significantly higher after Pentasa, reflecting the more proximal release of 5-aminosalicyclic acid compared with Salazopyrin. No relation was found between the 5-aminosalicylic acid fecal water concentration water concentration and the 5-aminosalicylic acid dose per kilogram of body weight. The urinary excretion of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid was higher after Pentasa than after Salazopyrin (32% vs 25%). Dose interval plasma concentration curves showed low values after both preparations. Based on the concept that the fecal water concentration is decisive for the efficacy of 5-aminosalicylic acid in distal inflammatory bowel disease, Pentasa treatment offers a relevant alternative in cases of Salazopyrin intolerance or allergy in children. The higher systemic bioavailability from Pentasa warrants monitoring of the renal function.

Aminosalicylic Acids↗
PubMed1993

Very low intraluminal colonic pH in patients with active ulcerative colitis.

Intraluminal gastrointestinal pH was measured in seven patients with active ulcerative colitis (four male, three female). A radiotelemetry capsule was used, and its location was determined by fluoroscopy. Satisfactory measurements were obtained from six, in all of whom pH levels were normal in the stomach and small intestine. Three patients also had normal pH values in the colon. However, in the remaining three patients very low pH levels (lowest values 2.3, 2.9, and 3.4) were found in the proximal parts of the colon. Five of the seven patients, including the three with low pH in the colon, underwent colectomy. The mechanism behind the low intraluminal pH in some patients with ulcerative colitis is speculative. Increased fecal concentrations of lactate occur in active disease, but some of the pH values measured in our study were below the pKa value of lactate. The study demonstrates that very low intraluminal pH levels in the colon occur in some patients with active ulcerative colitis. This might be an indicator of severe activity of the disease.

Adult↗
PubMed1991

Availability of mesalazine (5-aminosalicylic acid) from enemas and suppositories during steady-state conditions.

The local and systemic bioavailability of a mesalazine enema (Pentasa, Ferring A/S, Denmark) and a mesalazine suppository (Pentasa, Ferring) was assessed during steady-state conditions. Eleven healthy subjects took 1 g of the enema or the suppository twice daily for 1 week, with a drug-free period of at least 1 week in between. At the end of each treatment period the urine and faeces were collected for 48 h, and the concentrations of mesalazine and the metabolite acetyl-mesalazine were measured. Plasma concentrations of drug and metabolite were measured hourly during a 12-h dose interval. The faecal water concentration of mesalazine was significantly higher after suppository treatment (55.7 mmol/l) compared with enema treatment (31.7 mmol/l) (p less than 0.01). The systemic absorption was low; 15% of daily mesalazine dose was recovered in urine after enema treatment and 10% after suppositores (p less than 0.01). Plasma concentrations were low, and no accumulation of either mesalazine or acetyl-mesalazine occurred. In conclusion, the enema and the suppository can be continuously administered as 1 g of mesalazine twice daily, respectively, giving high faecal water concentrations of mesalazine and a low systemic absorption.

Administration, Rectal↗
PubMed1990

Measurement of gastrointestinal pH and regional transit times in normal children.

Gastrointestinal pH and regional intestinal transit times of a capsule were measured in twelve healthy children aged 8-14 years using a radiotransmitting pH-sensitive capsule. The location of the capsule was determined by fluoroscopy. pH in the stomach was 1.5, but rose to 6.4 in the duodenum (mean values). pH gradually rose in the small intestine and reached an alkaline peak value of 7.4 in the distal part. pH dropped to 5.9 in the cecum but rose to 6.5 in the rectum. Median gastric residence time of the capsule was 1.1 h. Small intestinal transit time was 7.5 h, and colonic transit time was 17.2 h. pH profile and intestinal transit times found in the present study are almost identical to values found in studies on healthy adults. It is therefore concluded that the release pattern of pH-dependent sustained-release tablets in children is likely to be equal to that of adults.

Adolescent↗
PubMed1990

Gastrointestinal pH and transit times in healthy subjects with ileostomy.

Gastrointestinal pH in 11 healthy subjects with ileostomy was determined with a pH-sensitive, radiotransmitting capsule. Median pH was 7.0 in duodenum, dropped to pH 6.3 in the proximal part, but rose to 7.3 in the distal part of the small intestine. In five subjects the pH of the ileostomy effluents was determined with the pH capsule as well as with a pH meter. Median pH was 7.2 measured with the capsule and 7.4 with the pH meter. The difference between the results obtained with the two methods ranged from 0.1 to 0.3 pH units. The median gastrointestinal transit time of the capsule was 10.5 h (range 6.2-12.8 h). Gastric residence time was 0.6 h (range 0.2-3.8 h), and small intestinal transit time was 10.3 h (range 5.6-11.9 h). Thus the small intestinal transit time in ileostomates is slightly increased compared with values reported from studies on subjects with intact gut. However, no statistically significant correlation was found between the small intestinal transit time and the time elapsed after the creation of the ileostomy. We conclude that colectomy does not alter small intestinal pH but seems to increase the small intestinal transit time of single units.

Adult↗
PubMed1990

Topical and systemic availability of 5-aminosalicylate: comparisons of three controlled release preparations in man.

The bioavailability of three pure 5-aminosalicylic (5-ASA) preparations (Asacol, Claversal, and Pentasa) was studied in 8 ileostomy patients and 12 normal subjects after 6 days of treatment with 2000 mg 5-ASA. The local bioavailability, reflected by the 5-ASA concentration was thereby measured at two clinically relevant areas of the gut: at the entrance to, and the exit from the colon. Estimates of the systemic bioavailability were obtained from the urinary excretions and the plasma values of 5-ASA and Acetyl-5-ASA (Ac-5-ASA) during the three regimens. The three preparations studied are designed to release 5-ASA at different levels in the intestine, but there was no significant difference in the 5-ASA concentrations in the ileostomy effluents (Asacol 1.8 mmol/L, Claversal 3.4 mmol/L, Pentasa 2.0 mmol/L, median values). However, we found a smaller urinary excretion of 5-ASA and Ac-5-ASA (5.2% vs Claversal 27.9% and Pentasa 23.0%, median values of ingested daily dose) and a lower concentration of Ac-5-ASA in the ileostomy effluents after Asacol treatment (0.8 mmol/L, median value) which indicates a more distal release from this preparation compared with Claversal (2.4 mmol/L, median value) and Pentasa (5.5 mmol/L, median value). In normal subjects a higher faecal water concentration of 5-ASA was found after Asacol (9.8 mmol/L, median value) compared with Claversal (5.0 mmol/L, median value), whereas no difference between the faecal water concentrations of Ac-5-ASA was found (Asacol 21.5 mmol/L, Claversal 21.6 mmol/L, median values). This can be explained by a larger systemic absorption of 5-ASA from Claversal, and accordingly Claversal treatment resulted in the largest urinary excretion of 5-ASA and Ac-5-ASA (43.7% vs Asacol 35.6% and Pentasa 31.6%, median values of ingested daily dose). The high Ac-5-ASA concentration in the ileostomy effluents and in the faeces after Pentasa, and the low plasma values, indicate a slow 5-ASA release from this preparation throughout the small and large intestine. The results of the study indicate that Asacol is released in the distal part of the small intestine, that Pentasa is gradually released in the small and large intestine, and that Claversal shows an intermediate release pattern.

Administration, Topical↗