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Biomedical subjects

L K Li

Publications and source records attributed to L K Li.

At least 19 recordsLinked to original sources
PubMed2006

Human papillomavirus infection in Shenyang City, People's Republic of China: A population-based study.

To investigate the prevalence of, and risk factors for, cervical infection with human papillomavirus (HPV) in Shenyang City, People's Republic of China, we interviewed and obtained cervical cell samples from 685 women aged 15-59 years enumerated from local population lists. Human papillomavirus DNA was detected in cervical cell samples using a GP5+/6+-based PCR assay for 44 HPV types. Human papillomavirus prevalence was 16.8% overall and 13.6% among women without cervical abnormalities (16.6% and 12.4%, respectively, age-standardised to the world standard population), with no significant trends in HPV prevalence by age group. Of the 32 types identified, high-risk HPV types predominated in all age groups, HPV16 being the most common (3.4% of all women), followed by HPV52 (2.5%) and 58 (1.9%). Multiple-type infections accounted for 31.3% of all infected women. Not being married, reporting multiple sexual partners and husband's extramarital sexual relationships were all significantly associated with being HPV-positive. The disclosure of a relatively high HPV prevalence in Shenyang, in comparison with other worldwide populations, raises important questions concerning the prevention of cervical cancer in China, especially given the promising efficacy of prophylactic HPV vaccines.

Adolescent↗
PubMed1997

Enhanced collagen synthesis in cultured skin fibroblasts from insulin-dependent diabetic patients with nephropathy.

Excessive production and deposition of extracellular matrix proteins are characteristic features of diabetic nephropathy. This study tests the hypothesis that cells from diabetic patients who develop nephropathy have a disturbance in collagen metabolism compared with cells from diabetic patients without complications. Kinetics of overall collagen metabolism and total protein synthesis were examined in serially passaged, subconfluent, quiescent skin fibroblasts cultured in either normal (5 mM) or high (25 mM) glucose concentrations from 14 insulin-dependent diabetic (IDDM) patients with nephropathy; 14 IDDM patients without nephropathy matched for age, diabetes duration, and body mass index; and 14 healthy subjects. Fibroblasts were incubated in the presence of 2 microCi/ml [3H]proline, and after labeling the incorporation of [3H]proline into total protein, collagen (collagenase-sensitive material), and noncollagen proteins (collagenase-resistant material) was determined at different time points. Collagen degradation was determined in pulse-chase experiments by following the residual collagen-bound radioactivity after incubation for 8 h with 10 microCi/ml [3H]proline. In high glucose concentrations (25 mM), overall collagen synthesis (measured as [3H]proline incorporation into extracellular and intracellular collagenase-sensitive material) was significantly greater in the patients with nephropathy (mean +/- SEM after a 24-h labeling period: 7189 +/- 671 dpm/10(6) cells) than in the patients without (4341 +/- 267 dpm/10(6) cells; P < 0.01) or healthy control subjects (3836 +/- 234 dpm/10(6) cells; P < 0.01). No significant differences were observed in noncollagen protein production or in collagen degradation rates among the three groups of subjects. In the presence of normal glucose concentrations (5 mM), collagen synthesis was lower in all groups studied, but the differences between IDDM patients with nephropathy and those without remained unaltered. These results suggest that long-term cultured fibroblasts derived from diabetic patients with nephropathy exhibit an abnormality in collagen metabolism. Cells from long-standing diabetic patients without nephropathy have normal collagen metabolism. The increased collagen synthesis is likely to be intrinsic to those diabetic patients susceptible to nephropathy and may play an important role in the sclerotic processes that occur in the kidneys, arteries, and heart.

Adult↗
PubMed1994

Application of a bi-directional associative memory (BAM) network in computer assisted learning in chemistry.

A computer assisted learning software based on a bi-directional associative memory (BAM) network was developed. The software was implemented to assist students in associating the names of the elements in the periodic table with their chemical symbols. The use of the BAM facilitates the analysis and interpretation of students' responses. The software package can be modified easily as an educational tool for other disciplines.

Algorithms↗
PubMed1994

Molecular cloning of the common carp (Cyprinus carpio) rhodopsin cDNA.

A recombinant phage clone containing a 1584 nucleotides rhodopsin cDNA was screened from a carp retinal cDNA library. The inserted DNA consisting of a single open reading frame of 1062 nucleotides at positions 72 to 1133 encodes a 354 amino acid polypeptide. The deduced amino acid sequence of carp rhodopsin showed 95.7, 85.5 and 74.4% identity with that of goldfish, sand goby and lamprey, respectively. The sites of palmitoylation, glycosylation, disulfide bond formation and Schiff base formation in the putative rhodopsin are all conserved.

Amino Acid Sequence↗
PubMed1992

Intracellular pH and Na+/H+ antiport activity of cultured skin fibroblasts from diabetics.

Increased leucocyte Na+/H+ antiport activity has previously been demonstrated in both hypertensive subjects and Type 1 diabetic patients with nephropathy and may indicate a predisposition to hypertension in such diabetic patients. We have studied intracellular pH and Na+/H+ antiport activity in cultured skin fibroblasts from diabetic patients with and without nephropathy, together with non-diabetic controls to assess if such differences persisted in cultured cells. Fibroblasts from diabetic patients with nephropathy were significantly more alkaline [median (range): 6.90 (6.82 to 7.07)] compared to both normoalbuminuric diabetic patients [6.81 (6.75 to 6.89)] or normal controls [6.82 (6.77 to 6.93)] (P < 0.001 for both). This was associated with a raised Na+/H+ antiport activity in cells from patients with nephropathy when intracellular pH (pHi) was clamped to pH 6.5, without any differences in the maximal transport capacity of the antiport at pHi 6.2. Using both intracellular pH and Na+/H+ antiport activity at pHi 6.5, patients with nephropathy were separated from uncomplicated subjects with a sensitivity of 92% and a specificity of 100%. In conclusion, the raised Na+/H+ antiport activity in cells from patients with diabetic nephropathy persists despite passaging in vitro, thus indicating a heritable component, and results mainly from an increased apparent affinity of the antiport for intracellular H+.

Adult↗
PubMed1992

Na+/H+ antiport activity and cell growth in cultured skin fibroblasts of IDDM patients with nephropathy.

IDDM patients with incipient and overt nephropathy have been found to exhibit an overactivity of RBC sodium-lithium countertransport. To explore the physiological relevance of this finding, we measured the activity of Na+/H+ antiport in serially passaged cultured skin fibroblasts from IDDM patients with and without nephropathy and from normal, nondiabetic control subjects. Na+/H+ antiport activity (measured as the rate of amiloride-sensitive Na+ influx at pHi = 6.4, extracellular pH = 8.0, and [Na+] = 1 mM) was elevated significantly in IDDM patients with nephropathy compared with IDDM patients without nephropathy and nondiabetic control subjects (13.35 +/- 3.8 vs. 8.54 +/- 2.0 vs. 7.33 +/- 2.3 nmol Na+.mg protein-1.min-1; P less than 0.006 and P less than 0.001, respectively). A kinetic analysis of Na+/H+ antiport activity showed that the raised activity in IDDM patients with nephropathy was caused by an increased Vmax for extracellular Na+. Km values were similar in the three groups. pH-stimulated amiloride-sensitive Na+ influx also was higher under baseline conditions and after serum stimulation in cells from IDDM patients with nephropathy. pHi values were significantly higher, both during active proliferation and after 10-min exposure to serum, in cells from IDDM patients with nephropathy, compared with IDDM patients without nephropathy and nondiabetic control subjects. Serum-stimulated incorporation of [3H]thymidine into DNA was greater in IDDM patients with nephropathy than in the other two groups (35.7 +/- 18.9- vs. 17.4 +/- 7.5- vs. 11.9 +/- 8.7-fold stimulation above baseline; P less than 0.01 for both.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Increased sodium-lithium countertransport activity in red cells of patients with insulin-dependent diabetes and nephropathy.

Susceptibility to diabetic nephropathy may be related to a predisposition to arterial hypertension. We have studied the activity of sodium-lithium countertransport in red cells, a marker of risk for essential hypertension, in white European adults with insulin-dependent diabetes and diabetic nephropathy, a matched group of patients with diabetes without renal disease, and nondiabetic patients with renal disease. Measures of metabolic control and concentrations of plasma free insulin and growth hormone were similar in the two diabetic groups. The degree of impairment in renal function was similar in the diabetic and nondiabetic patients with renal disease. Body-mass index and plasma potassium concentrations were similar in all three groups. Diastolic blood pressure was elevated to a similar degree in the two groups with renal disease, as compared with that in the diabetic patients without renal disease. The rates of sodium-lithium countertransport in red cells were significantly higher in the diabetic patients with renal disease (mean +/- SD, 0.55 +/- 0.19 mmol of lithium per liter of red cells per hour) than in the diabetic patients without renal disease (0.33 +/- 0.16; P less than 0.005) and in the nondiabetic patients with renal disease (0.31 +/- 0.14; P less than 0.001). Predisposition to hypertension, as indicated by elevated sodium-lithium countertransport activity in red cells, may serve as a marker for the risk of renal disease in patients with insulin-dependent diabetes.

Adult↗
PubMed1988

Biofragmentable bowel anastomosis ring: comparative efficacy studies in dogs.

Three studies were conducted in a total of 178 dogs to determine the efficacy of a biofragmentable bowel anastomosis ring (BAR) composed of polyglycolic acid and 12.5% barium sulfate. Wound strength and healing of BAR, suture, and staple colonic anastomoses were compared for intervals of up to 1 year. The effect of systemic steroid treatment and BAR size on anastomotic wound strength and healing was also studied. The BARs fragmented at a mean time of 15.06 days postoperatively and were passed in the feces without injury. Wound strength was determined by measurements of the pressure required to burst the anastomosed colonic segment and measurements of the tension required to break 10 mm wide longitudinal strips of the anastomosed segment. The studies demonstrated that wound strength had progressed to a point where continued mechanical support (with sutures or staples) was no longer required by 14 days in both nontreated and steroid-treated dogs. Gross healing evaluations at 21 days and beyond showed no differences due to anastomotic method. Microscopic evaluations suggested that residual granulation tissue was less at the sites of BAR asastomoses than at sites of suture or staple anastomoses at the 1-year interval, suggesting that healing may be better with BAR than with standard methods of colon anastomosis.

Anastomosis, Surgical↗
PubMed1987

Age-dependent changes in the distribution and concentration of human lens cholesterol and phospholipids.

Analyses of total lipid in individual lenses 1.8-63 years of age indicate that both the cholesterol and the phospholipid concentrations have reached a high level of 10 and 14 micrograms/mg lens dry weight, respectively, after the first ten years of growth. Thereafter, the rate of phospholipid accumulation was greatly reduced to a value of 0.05 microgram/mg per year while that of cholesterol reduced to 0.19. Analyses of the distribution of lipid in successive lens fiber layers indicate that both the cholesterol and phospholipid levels increase in the entire lens between the age of 1.8 and 9 years. Older lenses showed a continuous increase in the accumulation of cholesterol in the deep cortical fibers, while little or no increase in phospholipid concentration was observed. These results indicate that the accumulation of lipids is greater than that of lens dry mass (protein) during the first decade of lens growth. Since more than 90% of lenticular lipids are associated with fiber cell membranes, these data suggest a gradual change in the differentiation of the newly formed secondary fibers from the epithelium during this period. Analyses of the phospholipid composition of the successive fiber fractions indicate that the major phospholipids of phosphatidyl ethanolamine (PE), phosphatidylserine (PS) and sphingomyelin maintained a uniform distribution in the 1.8- and 5-year-old lenses. While no change was observed with the cortical fibers, older lenses showed a gradual loss of PE and PS in the nuclear fiber up to 63 years of age. By the late teen years, nuclear PS can no longer be detected, while high levels of PE are maintained in lens nucleus. The disappearance of nuclear PE begins in the teen years and is completed by the age of 40. The decrease in PE and PS resulted in a continuous increase in the cholesterol/phospholipid ratio, a measure of membrane rigidity in the nuclear fiber in lenses 20 years of age and older. This decrease is also responsible for the exceedingly high rigidity of the nuclear fibers of lenses 60 years of age and older. Possible lamellar cholesterol organization in the lens fiber membrane is discussed.

Adolescent↗
PubMed1987

Age dependent lipid and protein changes in individual bovine lenses.

Successive fiber fractions isolated from individual bovine lenses were fractionated to examine changes in lens proteins and membrane lipids as a function of age. In calf lens of about 1.2 gm wet weight, cholesterol (C) is maintained at a level of 3.3 microgram/mg dry weight in the outer cortical 30% of the lens. In the inner cortex, a C content of 2.4 micrograms/mg was found that decreased somewhat to 2.1 micrograms/mg in the inner nuclear 20% of the lens. The almost linear decrease in phospholipid (P) content from 11.6 in the cortex to 1.7 micrograms/mg in the nucleus resulted in a cortex to nucleus increase in C/P ratio from 0.5 to about 2.0 (mol/mol). Compared to calf lenses, a low C level of 2.4 micrograms/mg was observed in the outer cortex of cow lenses (approximately 3.0 gm wet weight). No significant difference in C level was found between the calf and cow lenses either in the inner cortical or nuclear regions. The P level was reduced to 6 and 1.2 micrograms/mg in the outer cortex and nucleus of the cow lens, respectively. The low nuclear P content is responsible for the observed high C/P value of 3.6. The lower lipid content found in the cortex of older lens suggests an age dependent decrease in the amount of available membrane lipid to envelope the newly formed fibers. A cortex to nucleus increase in the amount of urea-soluble (US) protein fraction from about 6 to 14% of total fiber mass was observed with the calf lens. In the cow lenses, the nuclear US fraction accounts for almost 30% of the fiber.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1986

Changes in lens protein in concentric fractions from individual normal human lenses.

The water soluble (WS), urea soluble (US) and urea insoluble (UI) fractions from individual human lenses 1.8 to 65 years of age were isolated from concentric fiber layers. In lenses younger than 19 years, a uniform distribution in the amount of WS, US and UI fractions was found throughout the entire lens. These fractions represent 83, 11.5 and 5.5%, respectively, of the lens dry weight. This composition was observed with the cortical fibers of all lenses examined up to the 65-year old. In the nuclear fiber layers, the proportion of US protein gradually increases in the third to fourth decade of lens growth and appears to have reached a maximum representing 22-24% of the nuclear fiber mass in 50-year and older lenses. A large increase in the amount of the UI fraction to 30% of the fiber mass was observed in lenses between the 5th and 6th decade of lens growth. The change from the cortical to nuclear composition occurs in a narrow region of the lens which becomes more peripheral with aging. The cortical WS fractions were characterized by well defined polyacrylamide gel bands in sodium dodecyl sulfate (SDS). Those of the nuclear fibers were broadened, especially in the 27/29 and 16/18 kilodalton (KD) region. The disappearance of the 20/22 KD bands in the inner cortical and nuclear fibers cannot be accounted for by the small increase in protein insolubilization in these regions of lenses 40 years or younger.

Adult↗
PubMed1985

Membrane cholesterol and phospholipid in consecutive concentric sections of human lenses.

Lens membrane preparations have been shown to have a remarkable rigidity which increases in the inner nuclear region of the lens and has been correlated with the cholesterol (C)/phospholipid (PL) ratio. However, the distribution of these lipids in single lenses had not been determined. Utilizing a new technique for isolating consecutive layers of a human lens, lipid composition and contents of seven pairs of normal lenses from subjects ranging from 54 to 77 years old have been analyzed. It was found that the PL content remains relatively constant at 22-24 micrograms/mg through all but the nuclear 10-15% of the lens dry weight where it drops precipitously to about 7 micrograms/mg. The C distribution is more complex; the C content is at a low level of 14 micrograms/mg in the outer cortical 15-20%, rises to 25 micrograms/mg in the inner cortical 40-60% of the total lens weight, and drops to 12 micrograms/mg upon reaching the nucleus. Thus, the continuous increase in the lens C/PL ratio is due to the increase in C in the cortex and the large decrease in PL in the nucleus. Analyses of phospholipid and fatty acid composition in the different regions of the lens indicate significant differences. However, the abundance of mono-unsaturated fatty acids contributing to the rigidity of the membrane has only minor variation. The lens has a remarkably low overall lipid content of 4% and only 2% in the nuclear region. Calculation of the surface area of the nuclear fiber cell suggests that less than one-third of the membrane is made of PL bilayer. Thus, a mosaic of PL and C patches or some other type of structure involving membrane fusion must be present. Conversion of the % dry weight occupied by the concentric fiber fractions to their location on the lens axis in mm indicates that the nuclear 15% dry weight of the tissue occupies more than 50% of the axial length. This region contains the embryonic lens and the primary lens fibers. Similarly, the metabolically active outer 20% of the dry weight accounts for less than 10% of the visual axial length and contains cells undergoing terminal differentiation. Cataractous lenses have lipid distributions similar to those of the normal lenses suggesting that membrane lipid is either not involved in cataract formation or that the primary insult is localized in an undetectable small number of fiber cells.

Aged↗
PubMed1976

Human alpha-crystallin. I. The isolation and characterization of newly synthesized alpha-crystallin.

Studies of the incorporation of 14C amino acids into human lens proteins demonstrate that an alpha-crystallin fraction takes up more than six times as much radioactivity as any other lens protein. Based on analyses with a calibrated Bio-Gel A-1.5 m column, a molecular weight of 4.9 x 10(5) +/- 5 per cent was obtained for this protein while sedimentation equilibrium analyses indicated a weight average molecular weight, Mw, of 7.5 x 10(5) +/- 4 per cent at 10,000 r.p.m. Gel electrophoresis in sodium dodecyl sulfate revealed two components with molecular weights of 22,000 and 20,000, values similar to those found with calf alpha-crystallin. Alkaline urea gel electrophoresis indicated one major polypeptide with a mobility similar to the B2 chain of calf alpha-crystallin and two major bands with mobilities between those of the calf alpha-crystallin A2 and A1 chains. Amino acid analyses of this newly synthesized alpha-crystallin gave a composition which with a few exceptions is very similar to that of calf alpha-crystallin. All three major polypeptides contained 14C amino acids. However, from the present data, it cannot be determined whether the three polypeptides were independently synthesized or a rapid transformation produced one of the labeled polypeptides in the A region. There appears to be between three and four times as many presumptive A as B polypeptides.

Amino Acids↗