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Biomedical subjects

P Fong

Publications and source records attributed to P Fong.

At least 19 recordsLinked to original sources
PubMed1997

Ultrabithorax and Antennapedia 5' untranslated regions promote developmentally regulated internal translation initiation.

The 5' untranslated regions (UTRs) of the Drosophila Ubx and Antp genes were tested for their ability to promote cap-independent translation initiation. The Ubx and the Antp 5' UTR were inserted between the CAT and lacZ coding sequences in a dicistronic gene and tested for IRES activity in transgenic Drosophila. Northern analysis of the mRNAs showed the presence of the predicted full-length dicistronic mRNAs. High CAT activity was expressed from the first cistron from all of the dicistronic constructs introduced into the fly genome. The dicistronic transgenic strains bearing the Ubx and Antp IRES elements expressed significant levels of beta-galactosidase (betaGAL) from the second cistron whereas little or no betaGAL was expressed in the controls lacking the IRESs. In situ analysis of betaGAL expression in the transgenic strains indicates that expression of the second cistron is spatially and temporally regulated. Although the developmental patterns of expression directed by the Antp and Ubx IRESs overlap, they exhibit several differences indicating that these IRESs are not functionally equivalent.

Animals↗
PubMed1995

An empirical method for assessing social problem solving in schizophrenia.

The development of a multimethod social problem-solving battery for schizophrenia is described. The battery is unique in that empirical methods were used throughout its development. The battery includes components that tap skills for response generation and response evaluation. The behavioral components of social problem solving are assessed in an extended role-play format. Individuals with schizophrenia and bipolar disorder, as well as nonpatient controls, completed the social problem-solving battery and cognitive measures. Subjects in the schizophrenia group performed more poorly than controls on measures of the ability to generate and evaluate response alternatives, as well as on the role-play test. The two patient groups did not differ in performance on any of the social problem-solving components. Appropriateness of affect was the most powerful predictor of problem-solving effectiveness.

Adult↗
PubMed1994

Two highly homologous members of the ClC chloride channel family in both rat and human kidney.

We have cloned two closely related putative Cl- channels from both rat kidney (designated rClC-K1 and rClC-K2) and human kidney (hClC-Ka and hClC-Kb) by sequence homology to the ClC family of voltage-gated Cl- channels. While rClC-K1 is nearly identical to ClC-K1, a channel recently isolated by a similar strategy, rClC-K2 is 80% identical to rClC-K1 and is encoded by a different gene. hClC-Ka and hClC-Kb show approximately 90% identity, while being approximately 80% identical to the rat proteins. All ClC-K gene products are expressed predominantly in the kidney. While rClC-K1 is expressed strongly in the cortical thick ascending limb and the distal convoluted tubule, with minor expression in the S3 segment of the proximal tubule and the cortical collecting tubule, rClC-K2 is expressed in all segments of the nephron examined, including the glomerulus. Since they are related more closely to each other than to the rat proteins, hClC-Ka and hClC-Kb cannot be regarded as strict homologs of rClC-K1 or rClC-K2. After injection of ClC-K cRNAs into oocytes, corresponding proteins were made and glycosylated, though no additional Cl- currents were detectable. Glycosylation occurs between domains D8 and D9, leading to a revision of the transmembrane topology model for ClC channels.

Amino Acid Sequence↗
PubMed1993

Cell proliferation in prostatic adenocarcinoma: in vitro measurement by 5-bromodeoxyuridine incorporation and proliferating cell nuclear antigen expression.

We assessed cancer cell proliferation, a marker of the biologic activity of tumor cells, by evaluating bromodeoxyuridine (BrdUrd) incorporation and proliferating cell nuclear antigen (PCNA) expression. Prostatic carcinoma specimens (N = 48) were incubated in the presence of BrdUrd to label cells undergoing DNA synthesis, and immunocytochemical staining was performed with monoclonal antibodies to BrdUrd and PCNA and a standard indirect immunoperoxidase technique. The proportion of cells staining positively (labeling index or LI) for BrdUrd and PCNA was determined in 2 ways: by counting only high-power fields with the greatest concentration of stained cells (selected LI); or by counting cells in random fields (random LI). For BrdUrd the mean selected and random LIs were 3.08% and 1.62%, respectively; for PCNA they were 6.02% and 3.47%. Random and selected BrdUrd correlated well (r2 = 0.83), as did random and selected PCNA LIs (r2 = 0.86). However, a weaker correlation was noted when LIs of both techniques were compared, with the PCNA LI usually higher. The LIs of either technique correlated rather poorly with tumor grade and concentration of prostate-specific antigen, but correlated well with clinical stage as assessed by examination and imaging. In addition, either technique discriminated among tumors known to be pathologically confined (stages A and B) and those with extension to seminal vesicles (stage C) or metastatic to regional lymph nodes or bone (p < 0.019).

Adenocarcinoma↗
PubMed1992

Characteristics of long-term human thyroid peroxidase autoantibody secretion in scid mice transplanted with lymphocytes from patients with autoimmune thyroiditis.

We have explored scid mice as an in vivo model to study lymphocyte function and autoantibody production in patients with autoimmune thyroiditis and thyroid peroxidase (hTPO) autoantibodies. Patient's peripheral blood mononuclear cells (PBMC) were transplanted into scid mice via intraperitoneal injections and human immunoglobulin G (hIgG) and thyroid autoantibody levels in the murine sera were monitored for a minimum of 3 months after transplantation. Human IgG reached maximum serum levels of > 3,000 micrograms/ml (mean +/- SEM = 1,199 +/- 354 micrograms/ml) after an average of 6.5 weeks. In reconstituted mice (hereafter named At-Scid-hu) substantial titers of anti-hTPO of up to 0.51 (ELISA index, normal range < 0.02) were observed over a period of 1-2 months, followed by a gradual decline. Immunization of AT-Scid-hu mice with immunogenic, recombinant human hTPO (rec-hTPO) failed to enhance hTPO-Ab levels. Furthermore, there was no correlation between the magnitude of human IgG in the murine serum and concomitant levels of anti-hTPO. Murine thyroid function was unaffected by the transplantation of PBMC, as evidenced by normal serum thyroxine (T4) levels, and lack of specific pathologic changes in the thyroid. These data indicate, for the first time, the potential for longer-term human thyroid autoantibody secretion in the scid mouse reconstitution model allowing for further investigation of the regulatory factors inpinging on the human B cells surviving in the murine environment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The SCID-hu mouse and thyroid autoimmunity: characterization of human thyroid autoantibody secretion.

Severe combined immunodeficient (SCID) mice were injected with peripheral blood mononuclear cells (PBMC) from normal individuals and 14 out of 18 had detectable serum human (h) IgG (maximum levels providing a mean +/- SEM 934 +/- 213 micrograms/ml) and IgM (253 +/- 93 micrograms/ml) at 3-6 weeks after transplantation. Serum human immunoglobulin levels were maximum 6-12 weeks after transplantation and declined to low levels over the subsequent 5 months. Human B cells constituted up to 10% and human T cells up to 40% of cells in the peripheral circulation and spleens of these animals 2-3 weeks after transplantation, PBMC, or intrathyroidal (IT) lymphocytes, from 6 patients with Graves' disease and high serum levels of thyroid autoantibodies were transplanted into 30 SCID mice (Graves' SCID-hu). Although serum human immunoglobulins were observed in only low amounts in the animals receiving IT lymphocytes (n = 4), increased levels of hIgG or hIgM were more easily detectable in 19 Graves' SCID-hu mice that received PBMC. The Graves' SCID-hu mice had significantly lower mean levels of hIgG and hIgM than those observed following transplantation of normal PBMC (mean maximum 328 +/- 113 and 32 +/- 21 micrograms/ml, respectively). Six of these 19 mice had detectable human autoantibody to thyroid peroxidase (TPO, as microsomal antigen) between 3 and 8 weeks after transplantation, with titers ranging from 0.05 to 0.39 (normal SCID-hu serum less than 0.02 ELISA Index). No abnormal thyroid hormone (T4 and T3) levels or thyroiditis was seen when compared to normal SCID-hu mice. Immunization of reconstituted SCID mice with recombinant immunoactive human TPO antigen failed to initiate anti-TPO in normal PBMC-treated mice nor did it increase the titer of human anti-TPO in the anti-TPO positive animals. In conclusion we successfully established human thyroid autoantibody secretion in the SCID-hu mouse and characterized the transient nature of the model. Further studies will be required to achieve successful antigen presentation in this system.

Animals↗
PubMed1991

Potassium dependence of Na-Cl cotransport in dog tracheal epithelium.

In confluent primary cultures of dog tracheal epithelium, we tested whether Cl entry across the basolateral membrane is by cotransport with K. Two approaches were taken. First, we measured the inhibition of short-circuit current (Isc) by the K channel inhibitor, Ba2+. Consistent with Na-K-2Cl cotransport, maximal doses of Ba2+ inhibited five-sixths of Isc in tissues previously stimulated to secrete Cl; only two-thirds of Isc should be sensitive to Ba2+ if NaCl cotransport is the entry mechanism. Second, we measured basolateral 86Rb uptake and demonstrated inhibition by bumetanide, an inhibitor of Na-K-2Cl cotransport in other tissues. The degree of inhibition by bumetanide was consistent with the levels of Cl secretion measured as Isc. Uptake of 86Rb was also reduced by removal of Na or Cl, and under these conditions Rb uptake was not further inhibited by bumetanide. These results suggest that the process responsible for Cl entry across the basolateral membrane of tracheal epithelium during Cl secretion is Na-K-2Cl rather than Na-Cl cotransport.

Amiloride↗
PubMed1991

Recombinant human thyroid-stimulating hormone: initial bioactivity assessment using human fetal thyroid cells.

We have assessed the bioactivity of newly available recombinant human TSH (rec-hTSH) using human fetal thyroid cells, with the longer term aim of assessing its use for clinical applications. Rec-hTSH caused a consistent and dose-related increase in thyroid monolayer cell cAMP release and human thyroglobulin (hTg) secretion, confirming its bioactivity. Repetitive studies (n = 5) allowed us to derive an estimated biopotency for the rec-hTSH preparation examined of 5.6 IU/mg compared to 10 IU/mg for commercially available bovine TSH for human use. The rec-hTSH had a bioimmune ratio of 0.55, similar to that of purified pituitary hTSH standards, Furthermore, rec-hTSH induced thyroid epithelial cell growth, as evidenced by a decrease in thyroid cell doubling time from 54 +/- 2.1 to 31 +/- 1.7 h (P less than 0.005). Hence, rec-hTSH is a potent glycoprotein hormone preparation when measured in a homologous human thyroid cell culture system. Rec-hTSH could serve as a future definitive International Standard and has the potential for a useful diagnostic and therapeutic reagent.

Cell Division↗
PubMed1988

Chloride transport in apical membrane vesicles from bovine tracheal epithelium: characterization using a fluorescent indicator.

C1 transport in apical membrane vesicles derived from bovine tracheal epithelial cells was studied using the C1-sensitive fluorescent indicator 6-methoxy-N-(3-sulfopropyl) quinolinium. With an inwardly directed 50 mM C1 gradient at 23 degrees C, the initial rate of C1 entry (JC1) was increased significantly from 0.32 +/- 0.12 nmol.sec-1.mg protein-1 (mean +/- SEM) to 0.50 +/- 0.07 nmol.sec-1.mg protein-1 when membrane potential was changed from 0 to +60 mV with K/valinomycin. At 37 degrees C, with membrane potential clamped at 0 mV, there was a 34 +/- 7% (n = 5) decrease in JC1 from a control value of 0.37 +/- 0.03 nmol.sec-1.mg protein-1 upon addition of 0.2 mM diphenylamine-2-carboxylate. The following did not alter JC1 significantly (JC1 values given as percent change from control): 50 mM cis Na (-1 +/- 5%), 0.1 mM furosemide (-3 +/- 4%), 0.1 mM furosemide in the presence of 50 mM cis Na (-5 +/- 2%), 0.1 mM H2DIDS (-18 +/- 9%), a 1.5 pH unit inwardly directed H gradient (-7 +/- 7%), and 0.1 mM H2DIDS in the presence of a 1.5 unit pH gradient (4 +/- 18%). With inward 50 mM anion gradients, the initial rates of Br and I entry (JBr and JI, respectively) were not significantly different from JC1.JC1 was a saturable function of C1 concentration with apparent Kd of 24 mM and apparent Vmax of 0.54 nmol.sec-1.mg protein-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Performance of solid-state 48 detector gamma counter using solid phase total thyroxin and free thyroxin assays.

We evaluated the performance of an automated 48 detector KinetiCount gamma counter using solid phase reagents for total thyroxin (TT4) and free thyroxin (FT4). Interassay coefficients of variations (CV) for both total T4 and free T4 ranged from 5.4% to 13%. Between-method correlation coefficients were 0.9798 for TT4 and 0.8844 for FT4. Detection limits for TT4 and FT4 were 3 micrograms/l and 3 ng/l, respectively. TT4 was linear up to 200 micrograms/l. The recovery of TT4 was between 99 to 101%. A computer-stored standard curve for total T4 was stable over a 6-day period. The 48 counting chambers demonstrated stability over a 45-day period with no significant changes in counting efficiency (p greater than 0.5). Precision between the 48 chambers gave a CV of 1.6%. Crosstalk between chambers was less than 0.3% with count rates up to 80,000 cpm. We conclude that the KinetiCount immunoassay system using solid phase separation technology performs well and is suitable for routine clinical use.

Evaluation Studies as Topic↗