Biomedical subjects

W M Lee

Publications and source records attributed to W M Lee.

At least 37 records · Page 2Linked to original sources

PubMed2001

Mutagenesis of the peptidyltransferase center of 23S rRNA: the invariant U2449 is dispensable.

U2449 is one of many invariant residues in the central loop of domain V of 23S rRNA, a region that constitutes part of the peptidyltransferase center of the ribosome. In Escherichia coli, this U is post-transcriptionally modified to dihydrouridine (D) and is the only D modification found in E.coli rRNAs. To analyze the role of this base and its modification in ribosomal function, all three base substitutions were constructed on a plasmid copy of the rrnB operon and assayed for their ability to support cell growth in a strain of E.coli lacking chromosomal rrn operons. Both purine substitution mutations were not viable. However, growth and antibiotic sensitivity of cells expressing only the mutant D2449C rRNA was indistinguishable from wild type. We conclude that while a pyrimidine is required at position 2449 for proper ribosomal function, the D modification is dispensable.

Base Sequence↗

PubMed2001

Susceptibility of lean and obese Zucker rats to tumorigenesis induced by N-methyl-N-nitrosourea.

To address the possible involvement of hyperinsulinemia in breast cancer development, we have examined the susceptibility of lean and obese Zucker rats to N-methyl-N-nitrosourea (MNU)-induced mammary cancer. Fifty-day-old female lean or obese Zucker rats received intraperitoneal (i.p.) injections of 37.5 or 20 mg/kg MNU, respectively. We showed in separate experiments that these doses produce similar levels of DNA methylation in the mammary epithelial cells of the lean and obese animals. Over the course of 29 weeks following MNU treatment, half of the lean rats developed carcinomas of the mammary gland, demonstrating that they are of intermediate susceptibility to mammary tumorigenesis. During this period, the obese rats developed hyperinsulinemia and insulin resistance as expected. Although palpable tumors developed at a similar rate in the lean and obese rats, only 10% of the obese animals developed mammary carcinomas. The obese rats, however, developed a high incidence (63.3%) of epidermal cysts that occurred mainly in the region of the mammary glands. A 13.3% incidence of colon carcinomas was also found in the obese rats. These results suggest that the development of hyperinsulinemia does not render the obese Zucker rats more susceptible to mammary gland carcinogenesis. Our observation of colon carcinomas in obese, but not lean rats, however, is consistent with evidence that hyperinsulinemia promotes colon cancer in rodents and humans.

Alkylating Agents↗

PubMed2001

Relationship between sonographic and pathologic findings in epidermal inclusion cysts.

PURPOSE: We evaluated the sonographic findings in epidermal inclusion cysts and related them to the pathologic findings. METHODS: We retrospectively reviewed the sonograms and pathology specimens of 24 patients with pathologically proven epidermal inclusion cysts. We evaluated the lesions for shape, size, internal echogenicity, posterior sound enhancement, and presence of color Doppler signals. We classified the masses into 5 sonographic types according to their internal echogenicity. The relationship between the sonographic types and the pathologic findings was examined. RESULTS: The masses were ovoid or spherical in 17 cases (71%), lobulated in 5 (21%), and tubular in 2 (8%). The longest diameter ranged from 1 to 6 cm (mean, 3.1 cm). Twenty-three cases (96%) were associated with posterior sound enhancement. Color Doppler signals were absent in 20 cases, but some vascularity was noted in 4 ruptured epidermal cysts, in areas of granulation tissue. The most common sonographic type was a hypoechoic lesion with scattered echogenic reflectors (10 cases). Sonographic findings were related to the lamellation of keratin debris and the granulation tissue secondary to rupture. Most cases with a lobulated configuration (4 of 5) or color Doppler signals (4 of 4) were ruptured cysts. CONCLUSIONS: Epidermal inclusion cysts most often appeared sonographically as a hypoechoic mass containing variable echogenic foci without color Doppler signals. Ruptured epidermal cysts, however, may have lobulated contours and show color Doppler signals, mimicking a solid mass.

Adolescent↗

PubMed2001

Enhanced naphthalene solubility in the presence of sodium dodecyl sulfate: effect of critical micelle concentration.

Surfactants can increase the solubility of non-polar compounds, and have been applied in areas such as soil washing and treatment of non-aqueous phase liquids (NAPLs). This investigation explored the feasibility of removing vapor phase polycyclic aromatic hydrocarbon (PAH) from gases using an anionic surfactant. The solubility of vapor phase naphthalene was measured herein using gas chromatograph (GC) with a photon ionization detector (PID). The measurement results indicated that surfactant molecules were not favorable to micelle formation when temperatures increased from 25 degrees C to 50 degrees C. Regardless of whether solutions were quiescent or agitated, equilibrium naphthalene apparent solubility increased linearly with surfactant concentrations exceeding critical micelle concentration (CMC). The pH effects on naphthalene apparent solubility were small. Agitation increased naphthalene apparent solubility and lumped mass transfer coefficients. Furthermore, lumped mass transfer coefficients decreased with increasing surfactant concentration owing to increase in interfacial resistance and viscosity and decreased spherical micelle diffusion coefficients. Finally, the net absorption rate increased because the solubilization effects of micelles exceeded the reduction effects of mass transfer coefficient above the CMC. The enhanced naphthalene apparent solubility from the addition of surfactant can be expressed by an enrichment factor (EF). The EF value of naphthalene for the surfactant solution at 0.1 M with agitation at 270 rpm relative to quiescent water could reach 18.6. This work confirms that anionic surfactant can improve the removal efficiency of hydrophobic organic compound (HOC) from the gas phase.

Chromatography, Gas↗

PubMed2001

Suppression of tumorigenicity in human ovarian carcinoma cell line SKOV-3 by microcell-mediated transfer of chromosome 11.

To determine the pathogenic role of chromosomes 11 and 17 in the carcinogenesis of human ovarian cancers, neo(R)-tagged chromosome 11 or 17 was transferred from cell lines A9H11 or A9H17, respectively, into the ovarian carcinoma cell line SKOV-3 using microcell-mediated chromosome transfer. The chromosome transfer was verified by polymerase chain reaction detection of the neo(R) gene, fluorescence in situ hybridization detection of an extra chromosome 11, and microsatellite polymorphism detection of an exogeneous chromosome 11. Five SKOV-3/A9H11 hybrids and five SKOV-3/A9H17 hybrid clones were generated. For the chromosome 11 transfer, complete suppression of tumorigenicity was observed in four clones, (11)9-8 and 11(H)7-2, 11(H)8-3, and 11(H)7-2, 100 days post implantation. For the chromosome 17 transfer, no complete suppression of tumorigenicity was observed. However, an increased latency period ranging from 25 to 49 days in contrast to 7 days for the SKOV-3 parental line, and a significant reduction in tumor size was observed. There was no correlation between the in vitro growth rate and the tumorigenicity or length of latency period. Our results demonstrate functionally that chromosome 11 may carry a tumor suppressor gene(s) while chromosome 17 may carry a tumor growth-inhibitor gene(s) for the ovarian carcinoma cell line, SKOV-3.

Animals↗

PubMed2001

Cholestatic presentation of chronic hepatitis C: a clinical and histological study with a review of the literature.

Bile duct lesions are observed in the livers of chronic hepatitis C patients, but are inconstant and rarely associated with other features of chronic cholestasis and progressive bile duct injury or loss. We aimed to identify the clinical and biochemical characteristics of patients with chronic hepatitis C from our patient database presenting with prominent cholestatic features to determine if there is a correlation between histological evidence of bile duct injury and clinical or biochemical features observed in these patients. We retrospectively reviewed a hepatitis C database including 620 patients to identify those who presented with either alkaline phosphatase (AP) > or = 400 units/liter (normal 30-126 units/liter) or AP > or = 250 units/liter with pruritus. All patients were negative for anti-mitochondrial antibody (AMA). Appropriate exclusion criteria were used to exclude patients with other confounding factors. Histological features were compared with age- and sex-matched controls selected randomly from our hepatitis C database. Thirty-two patients were identified as meeting the above criteria. Twenty-four were excluded for the presence of other confounding factors and two for lack of liver biopsy. There were two men and four women. The mean age was 47 +/- 9 years. Four of the six presented with pruritus, which was severe in three. Liver biopsy showed evidence of moderate to severe fibrosis in all but one patient. Evidence of bile duct injury was seen in all patients and tended to be more severe than in controls. Bile ductular proliferation and mild ductopenia were the most commonly observed findings. A subset of patients with chronic hepatitis C may present with prominent cholestatic features. The majority of these patients present with pruritus and have histological evidence of bile duct injury, which may be progressive.

Adult↗

PubMed2001

Rabbit sex hormone-binding globulin: expression in the liver and testis during postnatal development and structural characterization by truncated proteins.

Although sex hormone binding globulin (SHBG) is found in the blood plasma of adult humans and rabbits and the gene is expressed in their livers, it is not detected in the plasma of adult rodents nor is it expressed in adult rodent livers. Thus the rabbit represents a good model to study the metabolism and function of SHBG in the blood. We have used a cloned rabbit SHBG cDNA to detect mRNA expression in rabbits during the postnatal period, and to construct truncated SHBG proteins for structure/function analysis. The SHBG mRNA appeared in the testis as early as 3 days after birth. The level increased gradually in abundance throughout postnatal development, and attained a maximum at 12 weeks of age when the gonads were fully matured. In contrast, SHBG mRNA in the livers of male and female animals increased to a maximum by 4 weeks of age, and were maintained at this level until 12 weeks before subsiding to the initial levels. The increase and decrease in SHBG mRNA levels in the liver were accompanied by similar changes in serum SHBG. This suggests that SHBG in the blood circulation comes from the liver and this might also provide a source of SHBG for the male reproductive tract before formation of the blood-testis barrier. To elucidate the minimal sequence of rabbit SHBG responsible for steroid-binding, a panel of 13 truncated SHBG proteins was constructed, expressed in Escherichia coli, and biochemically purified for study. It was shown that the complete protein sequence of rabbit SHBG was important for maintaining a stable steroid-protein complex. Unlike human SHBG for which a truncated protein of the first 206 residues of the 373 amino acid protein can still bind steroid, removal of 43 or more residues from the C-terminus of rabbit SHBG completely abolished steroid-binding.

Age Factors↗

PubMed2001

Efficacy and safety of pegylated (40-kd) interferon alpha-2a compared with interferon alpha-2a in noncirrhotic patients with chronic hepatitis C.

Administration of interferon (IFN) 3 times weekly in patients with chronic hepatitis C (CHC) is associated with low sustained responses, which may be, in part, related to this regimen's inability to maintain IFN concentrations sufficient to suppress viral replication. An enhanced IFN molecule produced by the covalent attachment of a branched 40-kd polyethylene glycol moiety to IFN alpha-2a (PEG[40kd] IFN alpha-2a) exhibits sustained absorption, a restricted volume of distribution, and reduced clearance compared with unmodified IFN alpha-2a. One hundred fifty-nine patients with CHC participated in a randomized, ascending-dose (45 or 90, 180, 270 microg) study comparing PEG(40kd) IFN alpha-2a administered once weekly with 3 MIU IFN alpha-2a administered 3 times weekly for 48 weeks to determine the most appropriate PEG(40kd) IFN alpha-2a dose for subsequent clinical trials. Efficacy was assessed by measuring hepatitis C virus (HCV) RNA following a 24-week treatment-free period. Sustained virological responses for PEG(40kd) IFN alpha-2a once weekly were 10% (45 microg; not significant), 30% (90 microg; P = .009), 36% (180 microg; P = .0006), and 29% (270 microg; P = .004), compared with 3% for the 3-times-weekly 3-MIU IFN alpha-2a regimen. The types and frequencies of adverse events and laboratory abnormalities were similar among all groups. In conclusion, once-weekly PEG(40kd) IFN alpha-2a was associated with a higher number of sustained virological responses compared with IFN alpha-2a 3 times weekly in patients with CHC, but had a similar safety profile. The 180-microg PEG(40kd) IFN alpha-2a dose appeared to be the optimal dose based on sustained virological response and its associated side-effect profile.

Adult↗

PubMed2001

Hepatitis B infection in patients with acute liver failure in the United States.

Occult hepatitis B virus (HBV) infection has been reported in 30% to 50% of patients with acute liver failure (ALF) in small case series. The aim of this study was to determine the prevalence of occult HBV infection in a large series of ALF patients in the United States and the prevalence of precore and core promoter variants in patients with ALF caused by hepatitis B. Sera from patients in the US ALF study and liver, when available, were tested using nested polymerase chain reaction (PCR) with primers in the HBV S and precore regions. PCR-positive samples were sequenced. Sera and/or liver from 139 patients (39 males, 100 females; mean age, 42 years) enrolled between January 1998 and December 1999 were studied. Twelve patients were diagnosed with hepatitis B, 1 with hepatitis B+C+D coinfection, and 22 had indeterminate etiology. HBV DNA was detected in the sera of 9 (6%) patients; all 9 had ALF caused by hepatitis B. HBV genotypes A, B, C, and D were present in 4, 3, 1, and 1 patients, respectively. Seven of these 9 patients had precore and/or core promoter variants. Liver from 19 patients were examined. HBV DNA was detected in the liver of 3 patients with ALF caused by hepatitis B, but in none of the remaining 16 patients with non-B ALF. Contrary to earlier reports, occult HBV infection was not present in this large series of ALF patients in the United States. HBV precore and/or core promoter variants were common among US patients with ALF caused by hepatitis B.

Acute Disease↗

PubMed2001

The effect of surfactants on the deliquescence of sodium chloride.

This study investigated the deliquescence of sodium chloride aerosol with surfactants at a retention time of 4.24 sec. Two surfactants used in this study, glutaric acid and pyruvic acid, are found in atmospheric aerosol and have a high hydrophile-lipophile balance (HLB) value. The experimental system consisted of a relative humidity conditioner, a tandem differential mobility analyzer (TDMA) and a scanning mobility particle sizing (SMPS) system. Results obtained from the observation of TDMA presented the deliquescence point of sodium chloride aerosol at 75% RH. In addition, the growth size of sodium chloride aerosol was observed to be 79.47 nm and the growth ratio was 77.94%, when the initial size of aerosol was 101.82 nm. Surfactants were internally mixed with sodium chloride at six different weight fractions, i.e. 2.5, 5, 10, 20, 40, and 60% by weight of surfactants in dry aerosol. Both surfactants apparently decreased the deliquescence point of sodium chloride, in which the lowest deliquescence point appeared at about 71% RH when the weight fraction of surfactants is 60% by weight of surfactants in dry aerosol. Moreover, the smallest size of sodium chloride aerosol with surfactants was 142.7 nm at 60% by weight of pyruvic acid in dry aerosol. Our results further demonstrate that the deliquescence point and size of sodium chloride aerosol with surfactants are related to the weight fraction of surfactants.

Aerosols↗

PubMed2001

Effect of relative humidity on mixed aerosols in atmosphere.

In this study, the effects of relative humidity on the deliquescent point and size of internally mixed aerosols diameter, NH4NO3 and (NH4)2SO4 were investigated using a Tandem Differential Mobility Analyzer (TDMA) with a relative humidity conditioner. The growth of mixed aerosols appears to have two deliquescent steps. The first one was at about 61.2-61.3%, but the second one was at around 77-78%. At the first deliquescence point, growth ratio at phase change was 7.5%, which agrees with the growth ratio of ammonium nitrate aerosol. Growth ratio of phase change at the second deliquescence point was about 20%, lower than the growth ratio of ammonium sulfate aerosol. In the relative humidity range of 80-85%, the growth ratio of the mixed aerosols reached 60%. In other words, it appears that growth ratio increases with the size of aerosol. Furthermore, a theoretical growth model of mixed aerosols was developed and applied to estimate the amount of composition of the mixed aerosols dissolved at each deliquescence point. The results also show that some of ammonium sulfate already dissolved at the first deliquescence point according to the theoretical growth model.

Aerosols↗

PubMed2001

Simultaneous absorption of vapor phase polycyclic aromatic hydrocarbon and carbon dioxide in anionic surfactant solutions.

The goal of this work was to investigate whether the solubility of vapor phase polycyclic aromatic compounds (PAHs) and CO2 in water could be enhanced by adding anionic surfactant during the absorption process. Naphthalene was the PAH surrogate and sodium dodecyl sulfate (SDS) was the anionic surfactant. A series of batch experiments in an absorption cell were performed at 50 degrees C with the surfactant concentration both lower than and higher than the critical micelle concentration (CMC). The experimental findings indicate that the CMC was not a function of pH at values of 3, 5 and 7. Furthermore, at surfactant concentrations less than the CMC, naphthalene apparent solubility increased slightly. On the other hand, the equilibrium naphthalene or CO2 apparent solubility increased linearly, in proportion to the surfactant concentration at concentrations greater than the CMC. This is due to the solubilization effect of micelles, which were formed by the surfactant at concentrations above the CMC. During simultaneous absorption of the two, the presence of CO2 only slightly decreased naphthalene apparent solubility, while the apparent solubility of CO2 was drastically reduced in the presence of naphthalene. As the magnitude of the micelle solubilization effect was greater than the reduction of the mass transfer coefficient in the presence of the surfactant, the total gas absorption rate increased. When the surfactant concentration was 0.1 M, the enrichment factor (the ratio of the solubility in surfactant solution to that in water) values of naphthalene both with and without CO2 increased to 9.05 and 8.60, respectively. These experimental findings demonstrate that anionic surfactant may be applied to increase the removal efficiency of hydrophobic compounds and CO2 through either a spray or packed tower.

Absorption↗

PubMed2001

A 22-amino acid synthetic peptide corresponding to the second extracellular loop of rat occludin perturbs the blood-testis barrier and disrupts spermatogenesis reversibly in vivo.

When Sertoli cells were cultured in vitro on Matrigel-coated bicameral units, the assembly of the inter-Sertoli tight junction (TJ) permeability barrier correlated with an induction of occludin expression. Inclusion of a 22-amino acid peptide, NH(2)-GSQIYTICSQFYTPGGTGLYVD-COOH, corresponding to residues 209-230 in the second extracellular loop of rat occludin, at 0.2-4 microM into Sertoli cell cultures could perturb the assembly of Sertoli TJs dose-dependently and reversibly. This peptide apparently exerts its effects by interfering with the homotypic interactions of two occludin molecules between adjacent Sertoli cells at the sites of TJs, thereby disrupting TJs, which, in turn, causes a decline in transepithelial electrical resistance across the Sertoli cell epithelium. When similar experiments were performed using a 22-amino acid myotubularin peptide, NH(2)-TKVNERYELCDTYPALLAVPAN-COOH (residues 156-177), no effects on the assembly of inter-Sertoli TJs in vitro were noted. When a single dose of this synthetic occludin peptide was administered to adult rats intratesticularly at 1.5-10 mg/testis, germ cells began to deplete from the seminiferous epithelium within 8-16 days. By 27 days, virtually all tubules were devoid of germ cells. This antispermatogenic effect was reversible, because germ cells progressively repopulated the epithelium thereafter. Treated testes were indistinguishable from normal or control testes by 68 days post-occludin peptide treatment when assessed using histological analysis. In contrast, control rats receiving either no treatment, vehicle alone, or a 22-amino acid synthetic peptide of myotubularin displayed no changes in the testicular morphology at all time points. The occludin peptide-induced germ cell depletion was also accompanied by a disruption of the blood-testis barrier (BTB) when assessed by micropuncture techniques quantifying [(125)I]-BSA in rete testis fluid and seminiferous tubular fluid following i.v. administration of [(125)I]-BSA through the jugular vein. These results illustrate that the occludin peptide-induced disruption of the BTB may possibly affect the underlying adherens junctions, which causes premature release of germ cells from the epithelium and reversible infertility.

Amino Acid Sequence↗

PubMed2001

Educating nurses to care for the dying in Hong Kong: a problem-based learning approach.

Caring for dying patients is an essential and major aspect of nursing care. However, previous studies have revealed that nurses felt uncomfortable and inadequate in dealing with the dying patients and their families. This study reports the effectiveness of a problem-based learning approach in death education among a group of registered nurses in Hong Kong. Three problems, with three segmented scenarios related to cancer nursing, were used. Students went through the problem-based learning process and documented their learning throughout the course in journals. A total of 72 sets of journals were collected and analyzed. The strategies of within case and cross-case analysis were employed. The within case analysis explored the learning development of students for each problem. The cross-case analysis compared and contrasted findings of the within case analysis. Three themes have been derived from the findings. They were: nurses acknowledging their emotions in facing death and dying, a need for the nurses to be better equipped in communication and counseling, and a holistic and family-centered approach to care. This study provides evidence showing that problem-based learning is an effective strategy to enhance nurses' self-awareness of death and dying issues, and to stimulate nurses to formulate a plan that addresses the physical, psychological, and social aspects of care. Findings also reveal that nurses need to take into account the particular reactions of death and dying in the Chinese culture when planning care.

Adult↗

PubMed2001

Chronic graft-versus-host disease after hematopoietic cell transplantation presenting as an acute hepatitis.

A variety of illnesses involving the gut and liver follow hematopoietic cell transplantation (HCT). A 20 yr-old white male developed severe acute hepatitis 36 wk (day 252) after matched, unrelated, allogeneic HCT for chronic myelogenous leukemia (CML). Mild skin graft-versus-host disease (GVHD) had occurred at about 20 wk (day 140) after transplant. Liver biopsy showed bile duct injury and a diffuse lobular injury pattern most consistent with a GVHD variant and not reminiscent of drug-induced or viral hepatitis. No findings suggestive of herpesvirus, adenovirus, or varicella-zoster virus were found. High-dose steroids resulted in marked improvement of his liver enzyme levels. We report this patient as representing the acute hepatitic presentation of chronic GVHD of the liver.

Acute Disease↗

PubMed2001

Mutation of host delta9 fatty acid desaturase inhibits brome mosaic virus RNA replication between template recognition and RNA synthesis.

All positive-strand RNA viruses assemble their RNA replication complexes on intracellular membranes. Brome mosaic virus (BMV) replicates its RNA in endoplasmic reticulum (ER)-associated complexes in plant cells and the yeast Saccharomyces cerevisiae. BMV encodes RNA replication factors 1a, with domains implicated in RNA capping and helicase functions, and 2a, with a central polymerase-like domain. Factor 1a interacts independently with the ER membrane, viral RNA templates, and factor 2a to form RNA replication complexes on the perinuclear ER. We show that BMV RNA replication is severely inhibited by a mutation in OLE1, an essential yeast chromosomal gene encoding delta9 fatty acid desaturase, an integral ER membrane protein and the first enzyme in unsaturated fatty acid synthesis. OLE1 deletion and medium supplementation show that BMV RNA replication requires unsaturated fatty acids, not the Ole1 protein, and that viral RNA replication is much more sensitive than yeast growth to reduced unsaturated fatty acid levels. In ole1 mutant yeast, 1a still becomes membrane associated, recruits 2a to the membrane, and recognizes and stabilizes viral RNA templates normally. However, RNA replication is blocked prior to initiation of negative-strand RNA synthesis. The results show that viral RNA synthesis is highly sensitive to lipid composition and suggest that proper membrane fluidity or plasticity is essential for an early step in RNA replication. The strong unsaturated fatty acid dependence also demonstrates that modulating fatty acid balance can be an effective antiviral strategy.

Blotting, Northern↗

PubMed2001

Transforming growth factor-beta3 perturbs the inter-Sertoli tight junction permeability barrier in vitro possibly mediated via its effects on occludin, zonula occludens-1, and claudin-11.

Throughout spermatogenesis, inter-Sertoli tight junctions (TJs) that create the blood-testis barrier in the rat must be disassembled and reassembled to permit the timely passage of preleptotene spermatocytes from the basal to the adluminal compartment of the seminiferous epithelium. However, the mechanism(s) and the participating molecules that regulate this event are largely unknown. Although there is no in vitro model to study the event and regulation of inter-Sertoli TJ disassembly, primary cultures of Sertoli cells in vitro can be used to study junction assembly. In this study, we sought to investigate whether cytokines are involved in the inter-Sertoli TJ assembly in vitro. Sertoli cells isolated from 20-day-old rats were cultured at a density of 0.5-1.2 x 10(6) cells/cm(2) on Matrigel-coated dishes or bicameral units for 8-9 days. The steady-state messenger RNA levels of basic fibroblast growth factor (bFGF), transforming growth factor (TGF)-beta2, and TGF-beta3 at different time points were assessed by semiquantitative RT-PCR. In selected experiments, the assembly of inter-Sertoli TJs was monitored by transepithelial electrical resistance measurement. It was found that there was no change in the expression of basic fibroblast growth factor throughout the entire culture period. However, there was a 2-fold reduction in the expression of TGF-beta2 and TGF-beta3 at the time inter-Sertoli TJs were being assembled. On days 5-8, after the inter-Sertoli TJs had been assembled, the Sertoli cell steady-state messenger RNA levels of TGF-beta2 and TGF-beta3 increased by as much as 3- and 6-fold, respectively, when compared with Sertoli cells on days 1-3 when TJs were being assembled. Also, it was found that recombinant TGF-beta3 added to Sertoli cells cultured in vitro at 1.2 x 10(6) cells/cm(2) on Matrigel-coated bicameral units perturbed the inter-Sertoli TJ permeability barrier dose-dependently. Moreover, the presence of TGF-beta3 also inhibited the transient and/or basal expression of several TJ-associated proteins, which include occludin, zonula occludens-1, and claudin-11 when inter-Sertoli TJs were being assembled in vitro. These results suggest that TGF-beta plays a crucial role in regulating the complicated biochemical events of junction assembly in the testis.

Amino Acid Sequence↗

PubMed2001

Primary hypothyroidism in dogs is associated with elevated GH release.

The pulsatile secretion patterns of GH were investigated in seven beagle bitches by collecting blood samples every 10 min for 6 h during euthyroidism and 1.5 years after induction of primary hypothyroidism. Hypothyroidism was induced by surgical removal of the thyroid gland and subsequent destruction of any remnant thyroid tissue by oral administration of sodium [(131)I]iodide. Some of the physical changes observed in the dogs with primary hypothyroidism mimicked those of acromegaly. During both euthyroidism and hypothyroidism GH was secreted in a pulsatile fashion. The mean (+/-s.e.m. ) basal plasma GH concentration was significantly higher (P=0.003) in the hypothyroid state (4.1+/-1.6 microg/l) than in the euthyroid state (1.2+/-0.4 microg/l). Likewise, the mean area under the curve (AUC) for GH above the zero-level during hypothyroidism (27.0+/-10.0 microg/lx6 h) was significantly higher (P=0.004) than that during euthyroidism (11.7+/-2.0 microg/l x 6 h). The mean AUC for GH above the baseline was significantly lower (P=0.008) during hypothyroidism (2.4+/-0.8 microg/l x 6 h) than during euthyroidism (4.5+/-1.8 microg/lx6 h), whereas there was no significant difference in GH pulse frequency. The mean plasma IGF-I level was significantly higher (P<0.01) in the hypothyroid state (169+/-45 microg/l) than in the euthyroid (97+/-15 microg/l). The results of this study demonstrate that primary hypothyroidism in dogs is associated with elevated basal GH secretion and less GH secreted in pulses. This elevated GH secretion has endocrine significance as illustrated by elevated plasma IGF-I levels and some physical changes mimicking acromegaly. It is discussed that the increased GH release in hypothyroid dogs may be the result of the absence of a response element for thyroid hormone within the canine pituitary GH gene and alterations in supra-pituitary regulation.

Animals↗