Biomedical subjects

D C Lin

Publications and source records attributed to D C Lin.

At least 37 records · Page 2Linked to original sources

PubMed1999

Determination of baroreflex gain using auto-regressive moving-average analysis during spontaneous breathing.

The heart rate component of the arterial baroreflex gain (BRG) was determined with auto-regressive moving-average (ARMA) analysis during each of spontaneous (SB) and random breathing (RB) protocols. Ten healthy subjects completed each breathing pattern on two different days in each of two different body positions, supine (SUP) and head-up tilt (HUT). The R-R interval, systolic arterial pressure (SAP) and instantaneous lung volume were recorded continuously. BRG was estimated from the ARMA impulse response relationship of R-R interval to SAP and from the spontaneous sequence method. The results indicated that both the ARMA and spontaneous sequence methods were reproducible (r = 0.76 and r = 0.85, respectively). As expected, BRG was significantly less in the HUT compared to SUP position for both ARMA (mean +/- SEM; 3.5 +/- 0.3 versus 11.2 +/- 1.4 ms mmHg-1; P < 0.01) and spontaneous sequence analysis (10.3 +/- 0.8 versus 31.5 +/- 2.3 ms mmHg-1; P < 0.001). However, no significant difference was found between BRG during RB and SB protocols for either ARMA (7.9 +/- 1.4 versus 6.7 +/- 0.8 ms mmHg-1; P = 0.27) or spontaneous sequence methods (21.8 +/- 2.7 versus 20.0 +/- 2.1 ms mmHg-1; P = 0.24). BRG was correlated during RB and SB protocols (r = 0.80; P < 0.0001). ARMA and spontaneous BRG estimates were correlated (r = 0.79; P < 0.0001), with spontaneous sequence values being consistently larger (P < 0.0001). In conclusion, we have shown that ARMA-derived BRG values are reproducible and that they can be determined during SB conditions, making the ARMA method appropriate for use in a wider range of patients.

Adult↗

PubMed1999

The antiviral nucleotide analogs cidofovir and adefovir are novel substrates for human and rat renal organic anion transporter 1.

Nephrotoxicity is the dose-limiting clinical adverse effect of cidofovir and adefovir, two potent antiviral therapeutics. Because renal uptake likely plays a role in the etiology of cidofovir- and adefovir-associated nephrotoxicity, we attempted to identify a renal transporter capable of interacting with these therapeutics. A cDNA clone was isolated from a human renal library and designated human organic anion transporter 1 (hOAT1). Northern analysis detected a specific 2.5-kilobase pair hOAT1 transcript only in human kidney. However, reverse transcription-polymerase chain reaction revealed hOAT1 expression in human brain and skeletal muscle, as well. Immunoblot analysis of human kidney cortex demonstrated that hOAT1 is an 80- to 90-kilodalton heterogeneous protein modified by abundant N-glycosylation. Xenopus laevis oocytes expressing hOAT1 supported probenecid-sensitive uptake of [(3)H]p-aminohippurate (K(m) = 4 microM), which was trans-stimulated in oocytes preloaded with glutarate. Importantly, both hOAT1 and rat renal organic anion transporter 1 (rROAT1) mediated saturable, probenecid-sensitive uptake of cidofovir, adefovir, and other nucleoside phosphonate antivirals. The affinity of hOAT1 toward cidofovir and adefovir (K(m) = 46 and 30 microM, respectively) was 5- to 9-fold higher compared with rROAT1 (K(m) = 238 and 270 microM, respectively). These data indicate that hOAT1 may significantly contribute to the accumulation of cidofovir and adefovir in renal proximal tubules and, thus, play an active role in the mechanism of nephrotoxicity associated with these antiviral therapeutics.

Adenine↗

PubMed1998

Chromosome arrangement within a bacterium.

BACKGROUND: The contour length of the circular chromosome of bacteria is greater than a millimeter but must be accommodated within a cell that is only a few micrometers in length. Bacteria do not have nucleosomes and little is known about the arrangement of the chromosome inside a prokaryotic cell. RESULTS: We have investigated the arrangement of chromosomal DNA within the bacterium Bacillus subtilis by using fluorescence microscopy to visualize two sites on the chromosome simultaneously in the same cell. Indirect immunofluorescence with antibodies against the chromosome partition protein Spo0J were used to visualize the replication origin region of the chromosome. Green fluorescent protein fused to the lactose operon repressor Lacl was used to decorate tandem copies of the lactose operon operator lacO. A cassette of tandem operators was separately inserted into the chromosome near the origin (359 degrees), near the replication terminus (181 degrees), or at two points in between (90 degrees and 270 degrees). The results show that the layout of the chromosome is dynamic but is principally arranged with the origin and terminus maximally apart and the quarter points of the chromosome in between. CONCLUSIONS: The use of cytological methods to visualize two chromosomal sites in the same cell has provided a glimpse of the arrangement of a bacterial chromosome. We conclude that, to a first approximation, the folding of the bacterial chromosome is consistent with, and may preserve, the linear order of genes on the DNA.

Bacillus subtilis↗

PubMed1998

Characterization of a prokaryotic SMC protein involved in chromosome partitioning.

smc of Bacillus subtilis encodes a homolog of eukaryotic SMC proteins involved in chromosome condensation, pairing, and partitioning. A null mutation in B. subtilis smc caused a temperature-sensitive-lethal phenotype in rich medium. Under permissive conditions, the mutant had abnormal nucleoids, approximately 10% of the cells were anucleate, and assembly of foci of the chromosome partitioning protein Spo0J was altered. In combination with a null mutation in spo0J, the smc mutation caused a synthetic phenotype; cell growth was slower and approximately 25% of the cells were anucleate. Our results demonstrate that the B. subtilis Smc protein, like its eukaryotic counterpart, plays an important role in chromosome structure and partitioning.

Bacillus subtilis↗

PubMed1998

Identification and characterization of a bacterial chromosome partitioning site.

We have identified a DNA site involved in chromosome partitioning in B. subtilis. This site was identified in vivo as the binding site for the chromosome partitioning protein Spo0J, a member of the ParB family of partitioning proteins. Spo0J is a site-specific DNA-binding protein that recognizes a 16 bp sequence found in spo0J. Allowing two mismatches, this sequence occurs ten times in the entire B. subtilis chromosome, all in the origin-proximal approximately 20%. Eight of the ten sequences are bound to Spo0J in vivo. The presence of a site on an otherwise unstable plasmid stabilized the plasmid in a Spo0J-dependent manner, demonstrating that this site, called parS, can function as a partitioning site. This site and Spo0J are conserved in a wide range of bacterial species.

Amino Acid Sequence↗

PubMed1998

Damping in reflexively active and areflexive lengthening muscle evaluated with inertial loads.

Damping in reflexively active and areflexive lengthening muscle evaluated with inertial loads. J. Neurophysiol. 80: 3369-3372, 1998. Studies of active areflexive muscle have shown that during a constant velocity stretch the increment in force elicited by an incremental length change falls dramatically after a few hundred micrometers of stretch, a finding labeled as "muscle yield." The mechanical behavior after the yield was like a viscous damper, in that force varied only with velocity. In light of these observations, our aims were to determine whether viscous properties are also evident under more physiological conditions, specifically under inertial loading, and to evaluate the damping action of reflexively intact compared with that of deafferented muscle. The active soleus muscle in a decerebrate cat was forcibly stretched by a simulated inertia with a specified initial velocity. We compared muscle length changes when afferent pathways were intact with those recorded after cutting the dorsal roots. Our findings were that areflexive muscle showed highly damped responses, with large changes in mean muscle length, indicative of high viscosity relative to stiffness. In contrast, reflexively active muscle produced lightly damped oscillations, with minimal changes in mean length, reflecting low viscosity and high stiffness. It appears that the stretch reflect modifies the relative contributions of elastic and viscous-like forces, maintaining elasticity, which in turn sustains oscillations. These differences highlight tradeoffs between positional and velocity regulation, in that elastic properties of reflexively active muscle promote oscillations with modest change in mean muscle length, whereas viscous-like properties of areflexive muscle produce damped responses, with poor positional regulation.

Algorithms↗

PubMed1997

Bipolar localization of a chromosome partition protein in Bacillus subtilis.

We have determined the subcellular localization of the chromosome partition protein Spo0J of Bacillus subtilis by immunofluorescence microscopy and visualizing fluorescence of a Spo0J-GFP fusion protein. Spo0J was associated with a region of the nucleoid proximal to the cell pole, both in growing cells dividing symmetrically and in sporulating cells dividing asymmetrically. Additional experiments indicated that Spo0J was bound to sites in the origin-proximal third of the chromosome. These results show that the replicating chromosomes are oriented in a specific manner during the division cycle, with the Spo0J binding region positioned toward the cell poles. Experiments characterizing cells at different stages of the cell cycle showed that chromosome orientation is established prior to the initiation of cell division. Our results indicate that there is a mechanism for orienting the chromosomes and that the chromosome partition protein Spo0J might be part of a bacterial mitotic-like apparatus.

Bacillus subtilis↗

PubMed1997

Bipolar localization of the replication origin regions of chromosomes in vegetative and sporulating cells of B. subtilis.

To investigate chromosome segregation in B. subtilis, we introduced tandem copies of the lactose operon operator into the chromosome near the replication origin or terminus. We then visualized the position of the operator cassettes with green fluorescent protein fused to the Lac1 repressor. In sporulating bacteria, which undergo asymmetric cell division, origins localized near each pole of the cell whereas termini were restricted to the middle. In growing cells, which undergo binary fission, origins were observed at various positions but preferentially toward the poles early in the cell cycle. In contrast, termini showed little preference for the poles. These results indicate the existence of a mitotic-like apparatus that is responsible for moving the origin regions of newly formed chromosomes toward opposite ends of the cell.

Bacillus subtilis↗

PubMed1995

Molecular cloning, expression, and mapping of the high affinity actin-capping domain of chicken cardiac tensin.

Tensin, an actin filament capping protein first purified from chicken gizzard, is localized to various types of adherens junctions in muscle and nonmuscle cells. In this paper, we describe the isolation and sequencing of tensin cDNA from a chicken cardiac library. The 6.3-kb chicken cardiac tensin cDNA encodes an open reading frame of 1,792 amino acids. Mammalian cells transfected with the chicken tensin cDNA expressed a polypeptide of approximately 200 kD recognizable by antibodies to chicken gizzard tensin. The expressed protein was incorporated into focal adhesions and other actin-containing structures in the transfected cells. To map the domain associated with tensin's high affinity, barbed-end F-actin-capping activity, bacterially expressed recombinant fusion proteins containing various segments of tensin were prepared and assayed for activity. The results of these experiments show that the high affinity capping domain (kD = 1.3 nM) lies within amino acid residues R1037-V1169. Additional studies on a shorter construct, S1061-H1145, showed that these 85 residues were sufficient for producing complete inhibition of actin polymerization and depolymerization. While this active domain is located within that of the "insertin" sequence (Weigt, C., A. Gaertner, A. Wegner, H. Korte, and H. E. Meyer. 1992. J. Mol. Biol. 227:593-595), our data showing complete inhibition of polymerization and shift in critical concentration are consistent with a simple barbed-end capping mechanism rather than the "insertin model." Our results also differ from those of a recent report (Lo, S. H., P. A. Janmey, J. H. Hartwig, and L. B. Chen. 1994. J. Cell Biol. 125:1067-1075), which concluded that their recombinant tensin has an "insertin-like" inhibitory effect on barbed-end actin polymerization, and that this activity is attributed to residues T936-R1037 (residues 888-989 in their numbering system). In our study, a fusion construct (N790-K1060) encompassing T936-R1037 had no significant effect on actin polymerization and depolymerization, even at high concentrations.

3T3 Cells↗

PubMed1995

[Comparison of multiple dosage bioavailability between phenylpropanolamine controlled release suspension and conventional tablet in healthy volunteers].

Compared studies between the pharmacokinetics of phenylpropanolamine (PPA) controlled release suspension (CRS) and that of PPA conventional tablet in 10 healthy volunteers showed that the maximal plasma concentration (Cmax), the minimal plasma concentration (Cmin) and the fluctuation index (FI) values were 169.06 +/- 7.76 ng.ml-1, 82.80 +/- 4.29 ng/ml-1 and 0.20 +/- 0.04 respectively for PPA CRS, 180.5 +/- 8.91 ng.ml-1, 76.18 +/- 5.97 ng.ml-1 and 0.81 +/- 0.07 respectively for the conventional tablet. The Cmax and FI of PPA CRS were significantly lower compared with those of the conventional tablet (P < 0.01) during steady state. The Cmin of PPA CRS was higher than that of the conventional tablet (P < 0.05).

Biological Availability↗

PubMed1993

Mechanical properties of cat soleus muscle elicited by sequential ramp stretches: implications for control of muscle.

1. Force changes in areflexive cat soleus muscle in decerebrate cats were recorded in response to two sequential constant velocity (ramp) stretches, separated by a variable time interval during which the length was held constant. Initial (i.e., prestretch) background force was generated by activating the crossed-extension reflex, and stretch reflexes were eliminated by section of ipsilateral dorsal roots. 2. For the initial 400-900 microns of the first stretch, the muscle exhibited high stiffness, classically termed "short-range stiffness." This high stiffness region was followed by an abrupt reduction in stiffness, called muscle "yield," after which force remained at a relatively constant level, achieving a plateau in force. This plateau force level depended largely on stretch velocity, but this dependence was much less than proportional to the increase in stretch velocity, in that a 10-fold increase in velocity produced < 2-fold increase in plateau force. 3. In experiments where the velocities of the two sequential ramp stretches were identical, the force plateau level was the same for each stretch, regardless of the time elapsed before the second stretch (varied from 0 to 500 ms). In contrast, measures of stiffness during the initial portion of the second stretch showed time-dependent magnitude reductions. However, stiffness recovered quickly after the first stretch was completed, returning to control values within 30-40 ms. 4. In one preparation, in which the velocities of the two sequential ramp stretches were different, the force plateau elicited during the second stretch exhibited velocity dependence comparable with that recorded in the earlier single velocity studies. Furthermore, muscle yield was still evident in the case where the force change was due solely to the change in velocity and where short-range stiffness had not yet recovered fully from the initial stretch. On the basis of these findings, we argue that the classical descriptions of short-range stiffness and yield are inadequate and that the change in force that has typically been called the muscle yield reflects a transition between short-range, transient elastic behavior to steady-state, essentially viscous behavior. 5. To examine changes in the muscle's mechanical stiffness during single ramp stretches, a single pulse perturbation was superimposed at various times before, during, and subsequent to the constant velocity stretch. The force increment elicited in response to each pulse decreased relative to the initial isometric value, remained essentially constant until the end of the ramp, and then returned to its prestretch magnitude shortly (30-40 ms) after stretch termination.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

[Bioavailability of a controlled-release suspension of phenylpropanolamine in healthy volunteers].

A high-performance liquid chromatographic analysis of phenylpropanolamine (PPA) in human plasma is presented. Using direct UV detection the method is sufficiently sensitive to 25 ng/ml for PPA. Single-dose pharmacokinetics of PPA in 10 healthy volunteers taking controlled release suspension (C) or tablet (T), each containing 150 mg PPA was compared. The study described here has shown that the (C) AUC(0-infinity)/(T) AUC(0-infinity) = 1.02 (P greater than 0.4). The controlled-release product of PPA is equivalent to PPA tablet.

Adult↗

PubMed1992

Nuclear morphometry and its prognostic significance in laryngeal squamous cell carcinomas.

The five parameters including nuclear area (NA), nuclear perimeter (NP), nuclear diameter (ND), axis ratio and nuclear roundness were evaluated with MIAS200 Image Analysis System (Sichuan University, Chengdu) in 45 patients with laryngeal primary squamous cell carcinoma, which were confirmed pathologically and operated on from January 1977 to October 1987. The results showed that NA, NP and ND are important prognostic indicators. The survival rate in patients with large nuclei (NA greater than 73 microns2, NP greater than 32.5 microns, ND greater than 12 microns) was significantly lower than that in those with small nuclei (NA less than 73 microns2, NP less than 32.5 microns, ND less than 12 microns) (P less than 0.0025). These findings strongly suggest that patients with laryngeal squamous cell carcinoma with large nuclei should be treated more aggressively.

Adult↗

PubMed1991

A quantitative analysis of pendular motion of the lower leg in spastic human subjects.

The purpose of this study was to examine gravity-induced oscillations of the lower leg in normal and spastic subjects, with a view towards evaluating a clinical test of spasticity called the "pendulum" test. Motivations for studying the pendulum test were to determine if realistic aspects of spasticity and neuromuscular control could be incorporated into a description of the motion, and to better understand the underlying neurophysiological disturbances in spasticity. For passive limb motion (in which no reflex excitation occurred), a second-order linear model did not provide an adequate description of the motion for either spastic or normal legs. Instead, system equations including nonlinear mechanical properties simulating asymmetries in the swing and amplitude dependent variations in stiffness and damping provided a more accurate description. For spastic limb motion (in which reflex excitation did occur), accurate simulation required components accounting for abnormal reflex activation, coinciding with the time course of EMG activation. These included increased stiffness and damping with their gains related to reflex EMG magnitude, and changes in the rest length of the stiffness. Comparison of numerical solutions of the equations with experimental data showed our nonlinear model simulated the motion accurately, with the variance accounted for usually exceeding 90%.

Aged↗

PubMed1989