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Biomedical subjects

J Lin

Publications and source records attributed to J Lin.

At least 775 records · Page 43Linked to original sources
PubMedDate not supplied

Preliminary observations on dissolution and bioavailability of triamterene-hydrochlorothiazide combination products.

The dissolution profiles of two brands of triamterene-hydrochlorothiazide (TRM-HCT) combination tablets and two brands of TRM-HCT combination capsules were studied using the USP paddle method at 100 rev min-1 in acid medium (0.1N). The tablets represent two products marketed in Germany, whereas the capsules represent the approved innovator's product and an unapproved generic product. The tablets dissolved almost 100 per cent in 15 min whereas the capsules dissolved less than 25 per cent in 60 min. A pilot bioavailability study was carried out in four normal healthy male volunteers. Urine samples were collected over a 48 h period and analysed for TRM, its major metabolite TRM-sulfate, and HCT using HPLC methods. The dissolution characteristics of TRM can be associated with the total drug excretion (absorption) of the product. On the other hand, the excretion (absorption) of HCT was independent of dissolution characteristics of the products. However, in TRM-HCT combination product, there appears to be a 50 per cent reduction in HCT excretion (absorption) when compared to the reported excretion (absorption) from a marketed single-entity product.

Biological Availability↗
PubMedDate not supplied

Apoptosis occurs in a new model of thermal brain injury.

Apoptosis has been implicated recently as a prominent response of the brain to a variety of insults, such as ischemia and trauma. In this study, we demonstrate that apoptosis is a prominent part of the brain's response to a thermal insult. To examine the brain's response to a thermal insult, a new model of thermal brain injury in the laboratory rat was developed. Water heated to 60 degrees C was passed over an area of thinned calvarium for 1 min. This resulted in an actual brain temperature of 47-48 degrees C. A uniform area of 2,3,5-triphenyl-tetrazolium chloride pallor was demonstrated and pyknotic neurons were seen in the area of injury by hematoxylin-eosin staining. Apoptosis was demonstrated by the characteristic DNA fragmentation seen by agarose gel electrophoresis, ApopTag in situ staining and electron microscopy. The findings of apoptosis were localized to the area of thermal injury and were time dependent, starting 6 h after the insult and peaking approximately 18 h after the insult. This represents one of the first demonstrations that apoptosis occurs in the brain in response to a thermal injury.

Animals↗
PubMedDate not supplied

Unusual liver MR findings of Wilson's disease in an asymptomatic 2-year-old girl.

We describe the unusual magnetic resonance (MR) findings of a case of Wilson's disease (WD) in an asymptomatic 2-year-old girl. Preenhanced computed tomography revealed multiple hyperdense areas in the liver. These lesions were hyperintense on T1-weighted and hypointense on T2-weighted MR images, results that might be ascribed to the paramagnetism of copper deposited in liver at a relatively early stage of the disease before severe liver cirrhosis had evolved.

Biopsy↗
PubMedDate not supplied

Pathophysiology of cataracts: copper ion and peroxidation in diabetics.

The concentration of copper ion in cataractous lenses was higher than that in clear lenses. The concentration of copper ion was significantly higher in subjects with diabetes (DM group) than in subjects without diabetes (control group). The concentration of Cu2+ ion was significantly greater than that of Cu+ ion in the DM group. Furthermore, the concentration of copper ion unconjugated to protein was higher than that of protein-conjugated copper ion. It is assumed that in the cataractous lenses of the DM group, a decrease in the reactivity of the copper-containing enzyme superoxide dismutase and an increase in hydrogen peroxide concentration leads to the generation of hydroxyl radicals from the Fenton's-type reaction. In diabetes, an increase in lenticular glucose induces glycation with the release of copper ion from copper-containing enzymes, thus increasing the concentration of lenticular copper ion. As a result, superoxide scavenging activity is reduced and peroxide lipid concentration is increased. This is assumed to result from the hyperactivity of the peroxidation cascade.

Adult↗
PubMedDate not supplied

Dynamics of influenza A drift: the linear three-strain model.

We analyze an epidemiological model consisting of a linear chain of three cocirculating influenza A strains that provide hosts exposed to a given strain with partial immune cross-protection against other strains. In the extreme case where infection with the middle strain prevents further infections from the other two strains, we reduce the model to a six-dimensional kernel capable of showing self-sustaining oscillations at relatively high levels of cross-protection. Dimensional reduction has been accomplished by a transformation of variables that preserves the eigenvalue responsible for the transition from damped oscillations to limit cycle solutions.

Antigenic Variation↗
PubMedDate not supplied

Direction-changing positional nystagmus: incidence and meaning.

Direction-changing positional nystagmus (DCPN) is a nystagmus that changes its direction with different body and head positions. Many authors consider that it indicates the presence of a central nervous system lesion. Of 1,196 patients whose abnormal electronystagmographic (ENG) traces were reviewed, 46 (3.8 per cent) showed DCPN. Of these, ten (22 per cent) had central neurologic diseases, 14 (30 per cent) had peripheral vestibular diseases, and for 22 (48 per cent) there was no definite clinical diagnosis. Nineteen patients (41 per cent) with DCPN had ENG findings suggesting a peripheral vestibular lesion, while only five (11 per cent) had ENG findings suggesting a central vestibular lesion. Four of 44 control subjects exhibited DCPN. Thus, the presence of DCPN does not necessarily indicate disease of the vestibular system and definitely does not localize the site of a lesion in the vestibular pathways, but more often indicates a peripheral vestibular site. As with spontaneous nystagmus, lack of suppression with fixation suggests a central lesion.

Adult↗
PubMedDate not supplied

Long survival with metastatic clear cell sarcoma of the Achilles tendon.

Clear cell sarcoma of tendons and aponeuroses is a rare tumor with a predilection for the lower extremities, particularly the foot. Although it is claimed to have a poor prognostic outlook, it is sometimes characterized by a slow clinical course. The authors report a case with a prolonged survival period of 7 years--5 years in the presence of multiple lung metastases.

Achilles Tendon↗
PubMedDate not supplied

Kinetics of simultaneous saccharification and lactic acid fermentation processes.

After pretreatment of corn cob by dilute acid, the lignocellulosic residue was used as raw materials for the simultaneous saccharification and lactic acid fermentation (SSLF). Because of the same optimal temperature and pH requirement as well as the anaerobic condition, the lactic acid fermentation is perfectly compatible with enzymatic hydrolysis of cellulosic materials. In the SSLF processes, the final concentration of lactic acid reached 33.97 g/L with a conversion ratio of 79% based on the consumed cellulose. A mathematical model is suggested to simulate the SSLF process with good agreement.

Adsorption↗
PubMedDate not supplied

N-oxygenation of primary amines and hydroxylamines and retroreduction of hydroxylamines by adult human liver microsomes and adult human flavin-containing monooxygenase 3.

Adult human liver microsomes catalyze the NADPH-dependent N-oxygenation of 10-N-(n-octylamino)-2-(trifluoromethyl)phenothiazine to the corresponding oximes through the intermediacy of the hydroxylamine. In the presence of adult human liver microsomes, the primary amine is stereoselectively converted to the cis-oxime, but addition of the alternative competitive substrate hydroxylamine hydrochloride apparently decreases the amount of aliphatic hydroxylamine retroreduction because an increase in oxime formation was observed. In the presence of hydroxylamine hydrochloride, however, the oxime product recovered was formed with very low stereoselectivity. Studies on the biochemical mechanism of oxime formation suggested that cis-oxime formation in the presence of adult human liver microsomes was largely dependent on the human flavin-containing monooxygenase (form 3). This conclusion is based on the effects of incubation conditions on product formation when compared to results observed in the presence of cDNA-expressed human FMO3. The retroreduction of the intermediate hydroxylamine was dependent on NADPH but was not catalyzed by human flavin-containing monooxygenase (form 3) or any one of seven prominent cytochromes P-450 that have been well-characterized in the human liver microsomes examined. The results suggest that aliphatic primary amines are efficiently sequentially N-oxygenated in the presence of human liver microsomes to hydroxylamines and then to oximes mainly by the human flavin-containing monooxygenase. Retroreduction of the intermediate hydroxylamine is apparently facilitated by a novel but as yet poorly characterized enzyme system that does not employ any of the currently known well-characterized cytochrome P-450 enzymes present in adult human liver microsomes.

Adolescent↗
PubMedDate not supplied

Numerical cognition: age-related differences in the speed of executing biologically primary and biologically secondary processes.

Groups of younger and older adults were administered numerical and arithmetical tasks that varied in the extent to which they assess evolved versus culturally specific forms of cognition, termed biologically primary and biologically secondary abilities, respectively. Componential analyses of solution times suggested that younger adults are faster than older adults in the execution of biologically primary processes. For biologically secondary competencies, a pattern of no age-related differences or an advantage for older adults in speed of processing was found. The results are consistent with the view that there has been a cross-generational decline in arithmetical competencies in the United States and are discussed in terms of models of age-related change in cognitive performance.

Adult↗
PubMedDate not supplied

Synthesis of new classes of boron-containing nucleotides.

Four different types of boron-modified nucleotides are reported: P-boranophosphorothioates, P-cyanoboranophosphates, P-boranomethylphosphonates, and P3'-N5'-boranophosphoramidates. Synthesis of dinucleoside borano-phosphorothioates and nucleoside P-borano-P-thiomonophosphates via a lithium sulfide method is described. The Li2S method also provides an alternative way to synthesize phosphorothioates through a dinitrophenyl P(V) phosphotriester precursor. The mechanism of Li2S substitution was investigated.

Boron Compounds↗
PubMedDate not supplied

Synthesis of a novel nucleic acid mimic: P-boranomethylphosphonate.

A new type of non-ionic nucleotide analogue with a doubly modified internucleotide linkage, P-boranomethylphosphonate, has been successfully synthesized and characterized. Dithymidine boranomethylphosphonate 5 is the first example of a P-boranomethylphosphonate compound; it is a highly lipophilic phosphodiester analog, which is almost totally resistant to both snake venom phosphodiesterase (SVPDE) and bovine spleen phosphodiesterase (BSPDE). P-boranomethylphosphonates are expected to be promising candidates for mechanistic, diagnostic and therapeutic applications.

Boranes↗
PubMedDate not supplied

Experimental cerebral vasospasm and cyclic adenosine monophosphate (c-AMP).

Blood induced acute and chronic cerebral vasospasm were studied in Rhesus monkeys by serial angiography. Two vasoactive agents were evaluated. In acute spasm, phosphodiesterase inhibition by Aminophylline consistently reversed the vasospasm. This agent alone was ineffective in chronic spasm and required the addition of Isoproterenol to produce reversal of vasospasm. It is proposed that cerebral vasospasm may be associated with a decrease of intracellular c-AMP in vascular smooth muscle which can be reversed by manipulation of the enzyme pathway involved. It is further proposed that c-AMP is a basic common pathway through which adrenergic vascular reactivities are mediated.

Aminophylline↗
PubMedDate not supplied

Today's dental student is training for tomorrow's elderly baby boomer.

We are constantly reminded of the exploding elderly population and the increasing demand to meet their needs. But do we fully understand and appreciate the impact that this fastest-growing segment of the population will have upon our profession? Whether we realize it or not, today's dental student is training for tomorrow's elderly baby boomer. The baby boomer generation is 76 million strong, representing 19 years worth of births spanning from 1946-1964. That makes the oldest baby boomer 55 years old and the youngest 37 years old. What does this all mean? That from 2011-2030, the age group of 65 years of age and older will make up approximately 22% of the population, vastly changing our patient population, not to mention a significant increase in patient load. The future holds promise for not only a busy career, but also potentially a financially rewarding one as well. To some extent, we are all going to be geriatric clinicians. There is little doubt that there will be a great demand for services in restorative dentistry, prosthodontic dentistry, endodontics, periodontics, oral surgery, and perhaps orthodontics. As the baby boomers benefited from fluoride and sanitation, more people have been able to maintain their dentition and health into their older years. Dental students graduating today will be only beginning the prime of their careers as the baby boomers make their introduction in full force in the year 2011.

Adult↗