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L C Yu

Publications and source records attributed to L C Yu.

At least 109 records · Page 6Linked to original sources
PubMed1992

Cloning of a candidate gene for ataxia-telangiectasia group D.

Transfection, with a human cosmid clone library, of an ataxia-telangiectasia (AT) cell line (AT5BIVA) from complementation group D previously resulted in the isolation of a cell line (1B3) with partially restored resistance to ionizing radiation. We rescued the integrated cosmid sequences within 1B3 and obtained two cosmid clones that contained overlapping DNA from chromosomal region 11q23, previously shown to be the region containing the AT gene(s) from three complementation groups. Isolation of an apparently full-length 3.0-kb cDNA from a HeLa cell library demonstrated a previously unidentified gene (ATDC) within these cosmid clones. The transfected copy of the ATDC gene in 1B3 is truncated at the 3' end but is a complete transcription unit, because of the presence of SV40 termination sequences within the adjacent cosmid DNA. After further screening of cosmid clones from a chromosome 11 library, we identified contiguous DNA that contained the missing portion of the gene. Southern blot analysis indicated that the ATDC gene is present in a single copy in the human genome; however, RNA blot analysis revealed mRNA of several sizes (1.8, 2.6, 3.0, 4.7, and 5.7 kb) that varied among different cell lines. Because no large rearrangements were detected in AT5BIVA cells by Southern or RNA blot analysis, any alteration in the ATDC gene in this cell line would involve a point mutation or a small rearrangement. Transfection of the AT5BIVA cell line with one of the cosmids partially restored radioresistance. Analysis of 100 X-radiation hybrid cell lines containing various fragments from the chromosomal region 11q23 showed that the ATDC gene is closely linked to THY1. The ATDC gene therefore lies outside the linkage region predicted to contain the AT gene(s) for complementation groups A and C, indicating a separate locus for the AT complementation group D gene.

Ataxia Telangiectasia↗
PubMed1992

The human enamel protein gene amelogenin is expressed from both the X and the Y chromosomes.

Amelogenins, a family of extracellular matrix proteins of the dental enamel, are transiently but abundantly expressed by ameloblasts during tooth development. Amelogenins seem to regulate the formation of crystallites during the secretory stage of enamel development, while they are specifically degraded during tooth-bud maturation. In this paper we report the characterization of the AMGX and AMGY genes on the short arms of the human X and Y chromosomes which encode the amelogenins. Our studies on the expression of the amelogenin genes in male developing tooth buds showed that both the AMGX and AMGY genes are transcriptionally active and encode potentially functional proteins. We have isolated genomic and cDNA clones from both the AMGX and AMGY loci and have studied the sequence organization of these two genes. Reverse transcriptase (RT)PCR amplification of the 5' portion of the amelogenin transcripts revealed several alternatively spliced products. The splicing pattern observed in the Y-derived mRNA varies from that of the X-derived mRNA. The promoter regions from both genes and the predicted amelogenin protein sequences are presented. This information will be useful for studying the molecular basis of X-linked amelogenesis imperfecta, for understanding the evolution and regulation of gene expression on the mammalian sex chromosomes, and for investigating the role of amelogenin genes during tooth development.

Amelogenin↗
PubMed1991

Parallel inhibition of active force and relaxed fiber stiffness in skeletal muscle by caldesmon: implications for the pathway to force generation.

In recent hypotheses on muscle contraction, myosin cross-bridges cycle between two types of actin-bound configuration. These two configurations differ greatly in the stability of their actin-myosin complexes ("weak-binding" vs. "strong-binding"), and force generation or movement is the result of structural changes associated with the transition from the weak-binding (preforce generating) configuration to strong-binding (force producing) configuration [cf. Eisenberg, E. & Hill, T. L. (1985) Science 227, 999-1006]. Specifically, in this concept, the main force-generating states are only accessible after initial cross-bridge attachment in a weak-binding configuration. It has been shown that strong and weak cross-bridge attachment can occur in muscle fibers [Brenner, B., Schoenberg, M., Chalovich, J. M., Greene, L. E. & Eisenberg, E. (1982) Proc. Natl. Acad. Sci. USA 79, 7288-7291]. However, there has been no evidence that attachment in the weak-binding states represents an essential step leading to force generation. It is shown here that caldesmon can be used to selectively inhibit attachment of weak-binding cross-bridges in skeletal muscle. Such inhibition causes a parallel decrease in active force, while the kinetics of cross-bridge turnover are unchanged by this procedure. This suggests that (i) cross-bridge attachment in the weak-binding states is specific and (ii) force production can only occur after cross-bridges have first attached to actin in a weakly bound, nonforce-generating configuration.

Actins↗
PubMed1991

Simple urodynamic evaluation of incontinent elderly female nursing home patients. A descriptive analysis.

We present a descriptive analysis of the functional, mental, and urodynamic status of a population of incontinent elderly female nursing home patients. One hundred fifty-five intermediate care female patients with a mean age of 85.5 years were identified as being incontinent of urine at least once daily. After urologic evaluation, each patient was classified into one of four categories: incontinence with normal cystometrogram 68 (44%), detrusor instability (DI) 52 (34%), stress incontinence (SI) 27 (17%), or overflow incontinence (OI) 7 (4%). Thirteen weeks later, patients were again studied using simple water cystometry. At follow-up evaluation, 45 patients (33%) had urodynamic findings which differed from the initial evaluation. Of these women, 10 with DI, 12 with SI, and 2 with OI were found to have normal cystometric parameters at the time of follow-up study, while 19 (14%) who initially had normal cystometric findings had evidence of DI (11) or SI (3). Strong correlation between urinary incontinence in patients with normal cystometric findings and moderate to severe cognitive impairment was present. Simple urodynamic evaluation did identify patients with SI and OI who might benefit from specific therapy. Urodynamic evaluation of incontinent elderly female nursing home patients is indicated and may provide direction for planning treatment strategies.

Activities of Daily Living↗
PubMed1991

X-ray diffraction testing for weak-binding crossbridges in relaxed bony fish muscle fibres at low ionic strength.

Equatorial X-ray diffraction patterns from single skinned fibres from bony fish muscle (turbot) were obtained with the fibres at 6 degrees C bathed in relaxing solutions of 170 down to 26 mM ionic strength. Diffraction patterns from rigor fibres were also obtained as controls. Unlike fibres from rabbit muscle, which show very clear evidence of substantial crossbridge formation at low ionic strength in what is mechanically a rapid equilibrium ("weak-binding") state (Brenner et al., 1982), diffraction patterns from bony fish fibres showed only a small change in relative peak intensities at low ionic strength (26 mM) compared with normal (170 mM) ionic strength. However, there was a slight ordering of the filament lattice at low ionic strength. The specimen temperature used (about 6 degrees C) was not far from the normal physiological temperature of the fish. Likewise, only a small change was seen by Xu et al. (1987) in patterns from frog fibres at low ionic strength at 2 to 6 degrees C. (Rabbit fibres previously studied, where large changes were seen at temperatures of 5 to 20 degrees C, were about 17 to 32 degrees C below physiological.) The I11/I10 ratio for fish fibres at 26 mM ionic strength was actually lower than that for rabbit even at normal ionic strength. This may be associated with an intrinsic structural difference between these muscles or alternatively with the disordering of the crossbridge helix in rabbit muscle found at low temperature by Wray (1987), and could support the view that rabbit fibres at 5 degrees C and normal ionic strength may already have a significant population of weak-binding crossbridges.

Animals↗
PubMed1991

Characterization of radial force and radial stiffness in Ca(2+)-activated skinned fibres of the rabbit psoas muscle.

1. When chemically skinned muscle fibres are activated by Ca2+ at an ionic strength of 170 mM, the spacing between the filaments has been shown to decrease with increasing force, suggesting that the cross-bridges can generate force not only in the axial but also in the radial direction. In the present study, radial force and radial stiffness of activated single skinned rabbit psoas fibres were studied by X-ray diffraction. The responses of the lattice spacing to changes in osmotic pressure by application of dextran T500, which is equivalent to force applied in the radial direction, was examined. The radial force generated by the attached cross-bridges was calculated, with the approximation that a negligible fraction of cross-bridges was attached in the relaxed muscle at the same ionic strength of 170 mM. 2. The active radial force was found to be a slightly non-linear function of lattice spacing, reaching zero at 34 nm. The radial force was compressive at lattice spacing greater than 34 nm and expansive at less than 34 nm. 3. The active axial force, on the other hand, was found to be much less affected by the application of dextran T500. Active axial force increased by 4% to a plateau at 4% dextran T500 and then decreased by 10% at 8% dextran T500. 4. While not under osmotic pressure, the radial force of the activated fibre was determined to be 400 pN (single thick filament)-1. This is of the same order of magnitude as the axial force. The radial stiffness was also comparable to the axial stiffness at 7 pN (thick filament)-1 (0.1 nm)-1. 5. The radial elasticity of the fully activated fibre differs significantly from that of the fibre in rigor. The radial stiffness exhibited by fibres in rigor was approximately five times higher, at 30 pN (thick filament)-1 (0.1 nm)-1 and the point where the radial force reached zero was 38 nm. 6. In the activated state, the point at which radial force reaches zero is independent of the level of Ca2+ activation, i.e. independent of the number of cross-bridges attached to actin in the force-generating state. We suggest that the zero-force point is equivalent to the equilibrium point of a spring and is an intrinsic property of the radial elasticity of the cross-bridge. 7. It is concluded that activated and rigor cross-bridges exhibit a spring-like property in the radial direction.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Urinary incontinence: nursing home staff reaction toward residents.

1. ISQ-SR is a reliable and valid tool to measure psychological stress associated with working with urinary incontinent patients. 2. ISQ-SR can be used to measure efficacy of continuing education programs aimed at reducing staff stress associated with urinary incontinence. 3. Eighty percent of the staff reported that they looked for ways to help patients with their incontinence all the time, but only 50% said that they felt comfortable working with urinary incontinent patients all of the time. 4. Sixty-three percent of the staff reported that they felt frustrated about working with urinary incontinence some of the time, indicating a need for continuing education.

Aged↗
PubMed1991

The susceptibility testing of 13 strains of Mycobacterium leprae to rifampicin and the determination of minimal effective dosage.

By use of the mouse footpad technique, the susceptibility testing of 13 strains of Mycobacterium leprae to rifampicin (RFP) and the determination of minimal effective dosage (MED) were carried out. Among these strains of M. leprae, 8 were obtained from previously untreated multibacillary leprosy patients and 5 from relapsed leprosy patients without using RFP previously. The results showed that the MED of all strains to RFP were less than or equal to 0.001% FRP in the diet, 5 strains being equal to 0.001%, 5 less than or equal to 0.0001%, 2 greater than or equal to 0.0003% and 1 less than or equal to 0.0003%. The results indicated that the MED value of RFP could be lower than that of other reports. Because the critical concentration of RFP for assessment of RFP-resistant strains is not well established a further study would be worthwhile. The results of the determination of sera RFP concentrations in mice administered the RFP diet were identical with that of Holmes' report. Five of the 13 strains also showed that the growth of bacilli were suppressed by 10 mg/kg RFP using the gavage method.

Animals↗
PubMed1990

Profile of urinary incontinent elderly in long-term care institutions.

This article presents a profile of incontinent elderly in long-term care institutions. One hundred thirty-three frail elderly women were recruited from seven nursing homes in central Pennsylvania for a three-year clinical trial to test the effectiveness of a behavioral therapy on urinary incontinence. All of the patients had more than one medical diagnosis. Eighty percent had cardiorespiratory conditions; the most prevalent diagnoses were cardiovascular diseases. Eighty percent had one or more neurological diseases, including "organic brain syndrome" (47%) and senile dementia (30%); 44% had arthritis/rheumatism. Half of the patients showed severe cognitive impairment; only 12% showed no cognitive impairment. Sixty-three percent were totally dependent; 68% used wheelchairs, 61% were chairbound; 50% had impairments in vision, one-third in hearing, and 14% in speech. Normal bladder capacity, absence of detrusor instability, and satisfactory bladder emptying, as evidenced by low residual urines, was found in 41% of the patients, suggesting that incontinence in this elderly group may not be a primary bladder problem, but rather that mental and physical disabilities may be a more important underlying cause of incontinence in these patients. An important finding in this study is that 34% of the patients had detrusor instability. It is theoretically possible that pharmacologic therapy with anticholinergic agents or imipramine could improve incontinence in this group. Five percent were found to have large residual urine volumes in association with high-capacity bladders suggesting overflow incontinence as the cause of their daily leakage. Pelvic relaxation and stress leakage was far less common in this elderly group of nursing home patients than in young and middle-aged women.

Activities of Daily Living↗
PubMed1990

Habenula as a relay in the descending pathway from nucleus accumbens to periaqueductal grey subserving antinociception.

This study explored the possibility of a relay at habenula for the descending neural pathway of antinociception. The latency of the escape response elicited by radiant heat on the snout of the rabbit was taken as index of nociception. (1) Microinjection of 20 micrograms of morphine into nucleus accumbens resulted in a one-fold increase in nociceptive threshold 20-40 min after the injection. This effect of morphine was markedly attenuated by naloxone or met-enkephalin antiserum administered to the nucleus habenula, suggesting that the release of met-enkephalin in habenula is essential for the antinociception induced by morphine injected into nucleus accumbens. (2) Injection of 10 micrograms of morphine into habenula produced a significant increase in escape response latency 20-40 min after the injection. This antinociceptive effect of morphine was attenuated by naloxone or muscimol, and enhanced by bicuculline methochloride administered to periaqueductal grey, suggesting that morphine may act on habenula to activate a descending neural pathway extending to periaqueductal grey to induce an antinociceptive effect, which seems to utilize endogenous opioid peptides and gamma-aminobutyric acid as its mediators. Taking together, the results suggest that habenula is an important relay in the descending neural pathway from nucleus accumbens to periaqueductal grey subserving antinociception.

Animals↗
PubMed1990

[The neural pathway from nucleus accumbens to amygdala in morphine analgesia of the rabbit].

The purpose of this study was to explore possible neural connections between the nucleus accumbens and amygdala involved in analgesia. The latency of the escape response elicited by radiant heat applied on snout of the rabbit was taken as an index for nociception. It was found that: (1) the analgesic effect elicited by intra-accumbens injection of morphine was attenuated dose-dependently by intra-amygdala administration of opioid antagonist naloxone, or antisera against met-enkephalin (ME) or beta-endorphin (beta-EP), suggesting the involvement of ME and beta-EP in the accumbens-amygdala connection; (2) the analgesia produced by intra-amygdaloid injection of morphine was not affected by naloxone administered to nucleus accumbens, suggesting a one-way connection between the two nuclei; (3) the analgesia of intra-accumbens injection of morphine was significantly attenuated by muscimol, the GABA receptor agonist, and enhanced by bicuculline methochloride, the GABA receptor antagonist injected into the same site where morphine was administered. The results suggest that the analgesic effect of morphine administered to the nucleus accumbens is mediated by the suppression of the GABAergic inhibitory neurons located within the nucleus.

Amygdala↗
PubMed1990

Cost effectiveness of training incontinent elderly in nursing homes: a randomized clinical trial.

This study used a randomized clinical trial with 133 incontinent elderly in seven nursing homes to evaluate the effectiveness of a behavioral training therapy and its cost implications. The training program lasted three months, and a 22-week follow-up period examined the durability of the treatment effect. The therapy became effective after six weeks of training. By the final months of training, the treatment participants' wet episodes had been reduced by 0.6 episode per day, or a 26 percent reduction over baseline, and improvement was maintained during the follow-up period. Trainees with a high frequency of incontinence during baseline, relatively more cognitive residents, and residents with a normal bladder capacity responded better to this behavioral program. The cost of training was the equivalent of about one hour of nursing aide time per patient day. The reduction in incontinence during the follow-up period resulted in some small savings in laundry costs and supplies used, and some quantitatively unmeasurable but detectable improvement in psychosocial well-being among the trainees. Since the central figure in implementing this training protocol is the nursing aide, it is important to find an organizational management scheme that will stimulate nursing aides to reduce incontinence among nursing home residents.

Aged↗
PubMed1990

Preliminary observations on experimental leprosy in tupaias (Tupaia belangeri yunalis).

The Tupaia belangeri yunalis (tree shrew) is one of the primitive primates. They were inoculated subcutaneously in the footpad or intravenously with Mycobacterium leprae from a patient with multibacillary leprosy. As controls, the footpads of CFW mice were inoculated with the same suspension of M. leprae. The results showed growth of acid-fast bacilli (AFB) in the footpads of locally inoculated CFW mice and in the footpads of both locally and intravenously inoculated tupaias. Whereas the numbers of AFB declined in the footpads of CFW mice after 12 months, they increased in the tupaia footpads, up to 2.44 x 19(9) AFB/g of tissue. The footpads of one tupaia were swollen, which on section revealed a granulomatous infiltration, including foamy and heavily infected macrophages. M. leprae were also seen in the branches of cutaneous nerves. Also AFB occurred in some viscera. Preliminary studies indicate that the AFB multiplying in tupaias are M. leprae.

Animals↗
PubMed1989

A clinical trial of a behavioral therapy to reduce urinary incontinence in nursing homes. Outcome and implications.

One hundred thirty-three incontinent women in seven nursing homes were assigned randomly to a 13-week behavior therapy program for urinary incontinence or to a control group that received usual incontinence-related care. The therapy became effective after 6 weeks of training. By the final month of training, the treatment women's wet episodes had been reduced by 0.6 episodes per day, a 26% reduction over baseline. This reduction in the number of wet episodes was statistically significant, both with respect to this group's baseline levels of incontinence and in comparison with the performance of the control women. The number of wet episodes in the control group remained about the same throughout training and the 22-week follow-up period. The treatment women improved partly because they learned to request help, a response prompted and reinforced by the program. Trainees with a high frequency of incontinence during baseline, the more cognitively intact residents, and residents with normal bladder capacity responded better to this behavior therapy program.

Aged↗
PubMed1989

Analysis of equatorial x-ray diffraction patterns from skeletal muscle.

Some of the factors that affect the intensities and the phases of the first five equatorial x-ray reflections from skeletal muscle are studied by simplified models describing axially projected mass distributions in unit cells. Examples of mass distributions that produce various phase combinations and intensities are presented. Effects due to radial movement of crossbridges and those due to mass transfer between the thick filament and the thin filament regions are compared. In addition, the study suggests that some features in the reconstructed filament structures could be due to the consequences of limited resolution.

Animals↗
PubMed1989

Structures of actomyosin crossbridges in relaxed and rigor muscle fibers.

It was shown previously that a significant fraction of the myosin crossbridges is attached to actin in the skinned rabbit psoas fibers under relaxed conditions at low ionic strength and low temperature (Brenner, B., M. Schoenberg, J. M. Chalovich, L. E. Greene, and E. Eisenberg. 1982. Proc. Natl. Acad. Sci. USA. 79:7288-7291; Brenner, B., L. C. Lu, and R. J. Podolsky. 1984. Biophys. J. 46:299-306). In the present work, the structure of the attached crossbridges in the relaxed state between ionic strengths of 20 and 100 mM, as compared with that in the rigor state, is further examined by equatorial x-ray diffraction. Mass distributions projected along the fiber axis are reconstructed based on the first five equatorial reflections such that the spatial resolution is 128 A. The fraction of crossbridges attached under relaxed conditions are estimated to be in the range of 30% (at 100 mM ionic strength) and 60% (at 20 mM). The reconstructed density maps suggest that in the relaxed state, upon attachment the part of the crossbridge that centers around the thin filament is small, and the attachment does not significantly alter the center of mass of the myosin head distribution around the thick filament backbone. In contrast, accretion of mass in the rigor state occurs in a wider region surrounding the thin filament. In this case, mass in the surface region of the thick filament backbone is shifted slightly outward, probably by approximately 10 A. A schematic model for interpreting the present data is presented.

Actomyosin↗