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Biomedical subjects

S Lai

Publications and source records attributed to S Lai.

At least 127 records · Page 7Linked to original sources
PubMed1995

An additional 5'-upstream exon exists in the human pleiotrophin-encoding gene.

A 2-kb 5' fragment of hPTN (human pleiotrophin-encoding) genomic DNA was sequenced. Within this region we identified a new, upstream exon (U2). Cloning and sequencing of the PCR products of cDNAs from a human melanoma cell line revealed that a 401-bp intron was spliced out between exon U2 and a previously described untranslated exon U1. Our analysis also revealed that previously reported transcription start points (tsp) of PTN are located within exon U1.

Base Sequence↗
PubMed1995

Risk factors for HIV-1 seroconversion among injection drug users: a case-control study.

OBJECTIVES: A nested case-control study was conducted in Miami, Fla, to determine risk factors associated with human immunodeficiency virus type 1 (HIV-1) seroconversion among injection drug users. METHODS: The study identified 21 incident cases of HIV-1 infection and 76 unmatched controls from two longitudinal cohorts of injection drug users. One cohort consisted of individuals who originally had been recruited from treatment centers; a second cohort was recruited from the "street." Logistic regression analyses that adjusted for age, gender, and race were performed. RESULTS: The final model determined that the primary independent risk factor that best explained the risk for seroconversion was sharing injection equipment in the year prior to conversion; a marginal risk factor was presence of sexually transmitted disease during this same period. CONCLUSIONS: Both an injection component and a sexual component play a role in seroconversion among injection drug users, although the injection component is much stronger.

Adult↗
PubMed1995

The effects of HIV on cognitive and motor development in children born to HIV-seropositive women with no reported drug use: birth to 24 months.

OBJECTIVE: This study documents delays in the mental and motor functioning of infants perinatally infected with human immunodeficiency virus (HIV) while controlling for confounding effects of prenatal drug exposure, ethnicity, socioeconomic status, and maternal separation and death. METHODS: The cognitive and motor development of 126 infants born to nondrug-using, HIV-seropositive Haitian women was assessed at 3-month intervals through 24 months of age using the Bayley Scales of Infant Development. By 18 months of age, 28 of the infants were diagnosed as HIV-infected, and the 98 uninfected infants served as a control group. The infected and uninfected infants did not differ with respect to mean gestational age, birth weight, ethnicity, or rates of maternal separation and death. RESULTS: By 3 months of age, the mean mental and motor scores of the infected infants were significantly lower than those of the uninfected controls. Furthermore, the initial differences between the two groups increased over time, as many of the infected infants became increasingly delayed. Although the infected infants tended to perform more poorly than the uninfected infants, nearly one third of the infected infants exhibited relatively normal cognitive development and half demonstrated relatively normal motor development. CONCLUSIONS: Over the first 24 months of life, the mean rate of development of HIV-infected infants is significantly slower than that of noninfected infants born to seropositive mothers. This occurs even when the effects are not confounded with those of prenatal drug exposure.

Adult↗
PubMed1995

Using a titanium mesh plate to reconstruct the orbital floor after an incompletely reduced zygomaticomaxillary complex fracture.

A 30 year-old male came to us for correcting his severe left enophthalmos five months after a facial trauma in a traffic accident. CT scan of his left orbit showed a greatly increased orbital volume, which was resulted from the incomplete reduction of left zygomaticomaxillary complex (ZMC) fracture, unrepaired medial and lateral walls, and improper restoration of the orbital floor with a silicone sheet. Also, the decreased ocular volume, due to the evisceration of the ruptured eyeball with intraocular silicone ball implantation, contributed to the patient's enophthalmos. Because the patient refused any kind of osteotomy for his incompletely reduced and malunion ZMC fracture in the procedures of orbital reconstruction, correction of his severe enophthalmos became very difficult if not impossible. Therefore, we used a piece of titanium mesh plate about 2.5 x 4 cm in size, and folded it into an L shape. The shorter part of the L-shaped plate was used to fix the whole plate by screwing it into the anterior surface of the inferior orbital rim. The longer part of the plate was used as a new orbital floor. To hold and push the intraocular implant upward and anteriorly, the longer part of the plate was adjusted to a level higher than the original floor level, and was bent upward gently in the posterior part. Postoperatively, the severe enophthalmos was markedly improved, and the patient was satisfied although an evident supratarsal sulcus was still present. After a follow-up of 18 months, no complication of migration, infection, or extrusion of the titanium mesh plate occurred.

Adult↗
PubMed1994

2D and 3D high resolution gradient echo functional imaging of the brain: venous contributions to signal in motor cortex studies.

Recent emphasis on high resolution gradient echo studies in functional imaging has led to the conclusion that there are likely three domains of response to the blood circulation in the brain when considering field inhomogeneity effects of the venous blood pre- and during activation. The first is a coherent effect due to large or macroscopic vessels on the order of the size of the voxel (ca 200-500 microns in most studies). These can lead to very large signal changes (up to 100%). The second is at the venule level (ca 50-200 microns) and is associated with smaller parenchymal changes (usually ca 10% or less). The third is at the capillary level and is associated with much smaller signal changes at 1.5 T and even up to 4 T. The actual signal changes depend on field strength and sequence design. In this paper, we present our experience in detecting the first two domains with 2D and 3D gradient echo imaging at 1.5 T. We find that high resolution enables visualization of the larger small veins in motor cortex studies and that, on occasion, it is possible to see the venule effects as well. We suggest a simple model to explain the large signal changes based on susceptibility changes and partial volume effects. Comparisons of the functional imaging data to this model and to MR angiographic studies are also shown as evidence of the venous sources of the susceptibility changes.

Brain↗
PubMed1994

Non-radioactive DNA probe and polymerase chain reaction procedures for the specific detection of Acanthamoeba.

Acanthamoebae are potential pathogens which can cause serious infections of humans. A non-radioactive rDNA probe and polymerase chain reaction (PCR) amplification procedures which are specific, rapid, sensitive and safe for the detection of Acanthamoeba have been developed. A restriction fragment (126 bp; ArDNA-a) from a variable region of the cloned 26S rDNA unit of Acanthamoeba castellanii (from plasmid pAR2) was labelled by biotinylation. Cells and DNAs were incubated with the labelled rDNA probe to define conditions providing the highest hybridization specificity for Acanthamoeba by both colorimetric and chemiluminescent assays. Four recent isolates of Acanthamoeba, Acanthamoeba polyphaga, various bacteria, Herpes simplex virus, other eukaryotic amoebae and human cell lines, were sources of DNA for testing. The rDNA probe was found to be highly specific for Acanthamoeba and is capable of directly detecting about 250 cells without prior DNA purification. PCR primers for this unique ArDNA-a fragment have also been designed. Amplification of the targeted sequence by PCR using those primers yielded a single product which was specifically generated for Acanthamoeba template DNA and not DNA from the other control cells. This PCR procedure provided increased sensitivity with the direct detection of as few as 10 Acanthamoeba cells.

Acanthamoeba↗
PubMed1994

Abnormal connectivity of the visual pathways in human albinos demonstrated by susceptibility-sensitized MRI.

We studied activation of the human visual cortex (VC) using susceptibility-sensitized MRI at 1.5 Tesla. Three albinos and six healthy controls underwent a series of monocular and binocular photic flash stimulation. Monocular stimulation in albinos caused predominant contralateral activation with a small, well-delineated area in the anterior part of the VC in the ipsilateral hemisphere. This finding was consistent with a chiasmal crossing anomaly in albinism. All controls had symmetric patterns of activation during monocular stimulation. Functional MRI represents a promising method for evaluation of the visual pathways in humans.

Adolescent↗
PubMed1994

Resistance to AZT and ddC during long-term combination therapy in patients with advanced infection with human immunodeficiency virus.

To ascertain whether combination therapy with zidovudine (AZT) and zalcitabine (ddC) delayed the emergence of AZT resistance, isolates of human immunodeficiency virus (HIV) were evaluated from 15 previously untreated patients with advanced HIV disease who received combination therapy. Eighteen sequential viral isolates were available from 15 patients who received > or = 6 months of combination therapy. Isolates from eight (73%) of 11 patients obtained between 24 and 48 weeks of therapy were AZT resistant [50% inhibitory concentration (IC50) > or = 0.45 microM; range, 0.45-2.0 microM]. Four of these eight patients yielded virus isolates that were highly AZT resistant (IC50 > 1.0 microM). No changes in ddC susceptibility were discerned. The median IC50 for ddC was 0.2 microM and ranged from 0.07 to 0.5 microM. The CD4 cell counts of patients with AZT-sensitive virus tended to have higher median areas under the curve (AUC) and greater increases compared with patients who had AZT-resistant virus. They also had higher means and ranges of the average CD4 cell counts at week 36 (p = 0.01) and week 48 (p = 0.04). These data would indicate that the previously described more sustained CD4 cell responses conferred by the addition of ddC to AZT therapy cannot be ascribed to delayed emergence of AZT resistance with combination therapy.

CD4-Positive T-Lymphocytes↗
PubMed1993

Identification of vascular structures as a major source of signal contrast in high resolution 2D and 3D functional activation imaging of the motor cortex at 1.5T: preliminary results.

We have measured the T2* signal response associated with cortical activation due to finger motion at 1.5 Tesla. Both thin slice 2D and 3D images show signal intensity changes which vary from 2% to 32% depending on volunteer, echo time, slice thickness, and in-plane resolution. The largest signal change occurred for the thinnest slices and highest resolution (2 mm3). This is consistent with reducing partial volume effects and a simple difference in phase between the intravascular signal and surrounding parenchyma. No inflow enhancement was seen on the 2D or 3D scans, confirming the nature of the signal difference for this approach was due to local field inhomogeneity effects. Using 3D imaging, multiple effects can be seen simultaneously. With a 3D MRA method, it was possible to locate the vessel that was the source of the T2* behavior; it was in each case a vein on the surface of the cortical parenchyma.

Brain↗
PubMed1993

Right ventricle-to-aorta conduit in pulmonary atresia with intact ventricular septum and coronary sinusoids.

A 20-month-old girl with pulmonary atresia, intact ventricular septum, and ventriculocoronary connections underwent successful interposition of a right ventricle-to-aorta conduit and Fontan operation. The patient initially had a modified Blalock-Taussig shunt at birth and subsequently a bidirectional Glenn shunt at 8 months of age. After Fontan and right ventricle-to-aorta conduit placement, the suprasystemic right ventricular pressure dropped to systemic levels without causing myocardial injury. Additionally, the right ventricular cavity enlarged. We believe that the use of a right ventricle-to-aorta conduit should provide a valuable alternative and improve the outlook of certain patients with pulmonary atresia, intact ventricular septum, and ventriculocoronary connections.

Cardiac Surgical Procedures↗
PubMed1993

[Preparation and structural elucidation of insularine-N-oxides].

Oxidation of insularine (I) with m-chloroperbenzoic acid yielded four insularine-N-oxides. Two of them are identical in every respect with our insularine-2 beta-N-oxide (II) and insularine-2' beta-N-oxide (III), two rare examples of naturally occurring head-to-tail bisbenzylisoquinoline N-oxides newly isolated from Cyclea sutchuenensis, which confirmed the structures of the two novel natural N-oxides. The other two are new compounds and their structures have been established as insularine-2' alpha-N-oxide (IV) and insularine-2 beta,2' beta-N, N-dioxide (V), on the basis of spectral data (UV, IR, 1HNMR, NOEDS AND MS) analysis.

Cyclic N-Oxides↗
PubMed1993

[Two novel bisbenzylisoquinoline alkaloids from Cyclea sutchuenensis Gagnep].

In addition to the known cycleanine (I) and d-isochondodendrine (II), two novel bisbenzylisoquinoline alkaloids named isocycleanine (III) and sutchuenensine (IV) have been isolated from the roots of Cyclea sutchuenensis Gagnep grown wild in Sichuan province, China. III was established as the epimer of I and IV, as a new type of head-to-tail bisbenzylisoquinoline alkaloid with two diarylether bridges in between C-8 to C-12' and C-12 to C-7' on the basis of physical constants and spectral data (UV, IR, EIMS, 1HNMR and NOEDS).

Alkaloids↗
PubMed1992

VACUOLAR-TYPE H+-TRANSLOCATING ATPases IN PLANT ENDOMEMBRANES: SUBUNIT ORGANIZATION AND MULTIGENE FAMILIES.

Acidification of endomembrane compartments by the vacuolar-type H+-translocating ATPase (V-ATPase) is vital to the growth and development of plants. The V-ATPase purified from oat roots is a large complex of 650x10(3 )Mr that contains 10 different subunits of 70, 60, 44, 42, 36, 32, 29, 16, 13 and 12x10(3 )Mr. This set of ten polypeptides is sufficient to couple ATP hydrolysis to proton pumping after reconstitution of the ATPase into liposomes. Unlike some animal V-ATPases, the purified and reconstituted V-ATPase from oat is directly stimulated by Cl-. The peripheral complex of the ATPase includes the nucleotide-binding subunits of 70 and 60x10(3 )Mr and polypeptides of 44, 42, 36 and 29x10(3 )Mr. Six copies of the 16x10(3 )Mr proteolipid together with three other polypeptides are thought to make up the integral sector that forms the H+-conducting pathway. Release of the peripheral complex from the native membrane completely inactivates the pump; however, the peripheral subunits can be reassembled with the membrane sector to form a functional H+ pump. Comparison of V-ATPases from several plants indicates considerable variations in subunit composition. Hence, several forms of the V-ATPase may exist among, and probably within, plant species. At least four distinct cDNAs encode the 16x10(3 )Mr proteolipid subunit in oat. Multiple genes could encode different subtypes of the H+ pump that are regulated by the developmental stage and physiological function specific to the cell or tissue type.

Journal Article↗
PubMed1992

Structure of the human heparin-binding growth factor gene pleiotrophin.

We report that the human gene coding for the heparin-binding growth factor pleiotrophin (PTN) spans more than 65 kb and contains at least 7 exons. Analysis of human genomic DNA fragments showed that the open reading frame (ORF) is located on 4 exons. The splice sites in the ORF coincide with the boundaries of functional domains in the human PTN protein and appear to be conserved in the mouse PTN and in the related family of midkine genes. The 5'- and the 3'-ends in the untranslated regions of the human PTN are distinct from those of other species and are highly homologous to the antisense cDNAs of heat shock protein 70 and of ribosomal protein L7 respectively. These two regions are located on separate exons and could play a role in the posttranscriptional regulation of human PTN gene expression.

Amino Acid Sequence↗
PubMed1992

An outbreak of tuberculosis caused by multiple-drug-resistant tubercle bacilli among patients with HIV infection.

OBJECTIVE: To evaluate a nosocomial outbreak of tuberculosis caused by multiple-drug-resistant bacilli among patients with tuberculosis and HIV infection. DESIGN: A case-control study. PATIENTS: Patients with HIV infection and culture-proven tuberculosis. MEASUREMENTS: Patient characteristics, date of diagnoses of HIV infection and disease, date of diagnosis of tuberculosis, Mycobacterium tuberculosis susceptibility results, and medical center contact. RESULTS: Sixty-two patients who had tuberculosis caused by multiple-drug-resistant bacilli (cases) and 55 patients who had tuberculosis caused by susceptible or single-drug-resistant bacilli (controls) were identified. Controls were more likely to be black (odds ratio, 0.4; 95% CI, 0.2 to 0.9) or Haitian (odds ratio, 0.2; CI, 0.1 to 0.6) compared with cases, who were more likely to be homosexual men (odds ratio, 2.9; CI, 1.3 to 6.4). Forty-four cases (71%) had previous contact with an HIV clinic compared with 15 controls (27%) (P less than 0.0001). Cases were more likely to have had AIDS (odds ratio, 7.7; CI, 1.5 to 53.7), to have been hospitalized on an HIV ward (odds ratio, 8.3; CI, 2.3 to 29.7), to have been seen in an HIV clinic (odds ratio, 7.8; CI, 3.4 to 18.1), to have received intravenous therapy in an HIV clinic (odds ratio, 13.0; CI, 4.6 to 37.0), or to have received inhalation pentamidine in an HIV clinic before a diagnosis of tuberculosis was made. Multiple logistic regression analysis showed that a diagnosis of AIDS (odds ratio, 11.2; CI, 3.1 to 40.6) and HIV clinic visits (odds ratio, 13.0; CI, 2.7 to 63.7) before a diagnosis of tuberculosis were significantly associated with tuberculosis caused by multiple-drug-resistant bacilli. Using susceptibility patterns and appointment dates, we found that 22 cases had previous contact with a person who had tuberculosis caused by multiple-drug-resistant bacilli in the HIV clinic. CONCLUSIONS: Nosocomial transmission of M. tuberculosis from other HIV-infected patients with tuberculosis caused by multiple-drug-resistant bacilli can occur. These findings have serious public health implications and demand strict adherence to acid-fast bacilli isolation precautions.

Adult↗