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Biomedical subjects

L Tan

Publications and source records attributed to L Tan.

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

Comparison of the ability of normal mouse mammary tissues and mammary adenocarcinoma to cleave rat prolactin.

Previous studies have shown that target tissues cleave rat prolactin (rPRL) to form a two-chain derivative that yields approximately 16- and approximately 6-kDa fragments upon reduction. Both cleaved rPRL and the purified 16-kDa fragment have novel biological activities. Thus, cleavage may be of physiological significance. We determined whether normal mammary tissue or stroma (lacking mammary epithelial cells [MEC]) or mammary tumor tissue could cleave rPRL in vitro. Tumor explants were derived from a transplantable mammary tumor cell line (TPDTMT-4EP). The hormone was incubated with explants of those tissues from female BALB/c or DDD mice. Medium samples were processed by SDS-PAGE, and the relative abundance of intact and cleaved rPRL was determined by densitometric analysis of immunoblots using an antiserum to the 16-kDa fragment of rPRL. After 2-hr of incubation, normal DDD mammary explants cleaved approximately 25% of added rPRL, but tumor explants cleaved none. Explants of intact virgin BALB/c mouse mammary gland and of parenchyma-free "cleared" mammary fat pad cleaved rPRL equally well, but explants of abdominal adipose tissue had low cleaving activity. Homogenates of cleared mammary fat pads that were incubated with rPRL contained a high proportion of the cleaved form but none of the free 16-kDa fragment. These results indicate that cleavage of rPRL is highly specific to mammary stroma. Such cleavage may yield a form of the hormone that has novel activities within the mammary gland or elsewhere in the body.

Adenocarcinoma↗
PubMed1995

[Simultaneous determination of verapamil and its major metabolite in human plasma by high performance liquid chromatography].

A sensitive high-performance liquid chromatographic assay suitable for the simultaneous determination of verapamil (I) and its major active metabolite norverapamil (II) in human plasma is described. After adding internal standard ethmosine, plasma samples were extracted using a mixture of n-hexane and n-butyl alcohol (12:1) to give mean recoveries of > 92% of both I, and II. The extracts were chromatographed on a C18 reversed phase column with a mobile phase composed of methanol, water and triethylamine (67: 33: 0.4, pH 6.7), with UV (lambda, 279 nm) detection. The calibration curves were linear over a wide range of concentrations (25-1000 ng.ml-1), and the limits of determination was 2.5 ng.ml-1 for I and 5.0 ng.ml-1 for II. The method showed good precision: the within-day RSD were < 7.6% for both I and II; the day-to-day RSD were < 8.6% for both I and II. Using this assay, plasma concentrations of both I and II were simultaneously determined in six volunteers after a single oral dose of 120 mg of verapamil.HCl.

Calcium Channel Blockers↗
PubMed1995

[Effect of acupuncture on the contents of enkephalins in different brain regions of rats with traumatic shock].

The study was carried out on the animal model of traumatic shock which induced by ligating bilateral hind legs. The contents of enkephalins in hippocampus, striatum, hypothalamus, diencephalon and brain stem were determined with radioimmunoassay. The results show that: (1) when traumatic shock occurs, the contents of Met-enkephalin are not obvious change in the above 5 brain regions, and also not significant change after acupuncture; (2) there is a tendency to increase the content of Leu-enkephalin in each brain region described above of shock animal, while it is decreased in hypothalamus after acupuncture. The result suggests that the occurrence of traumatic shock may be related to the functional activities of Leu-enkephalinergic system in the central nervous system; the anti-shock of acupuncture may be through a decrease in the level of central Leu-enkephalin to improve micro-circulation and raise the blood pressure.

Animals↗
PubMed1994

Gallinacins: cysteine-rich antimicrobial peptides of chicken leukocytes.

We purified three homologous antimicrobial peptides ('gallinacins') from chicken leukocytes, examined their antimicrobial activity in vitro, and established their primary sequences by a combination of gas phase microsequencing and on-line LC-ESI-MS analysis of endo- and exoprotease peptide digests. The peptides contained 36-39 amino acid residues, were relatively cationic due to their numerous lysine and arginine residues, and each contained 3 intramolecular cystine disulfide bonds. Gallinacins showed primary sequence homology to the recently delineated beta-defensin family, heretofore found only in the respiratory epithelial cells and neutrophils of cattle, suggesting that beta-defensins originated at least 250 million years ago, before avian and mammalian lineages diverged. The 9 invariant residues (6 cysteines, 2 glycines and 1 proline) common to avian gallinacins and bovine beta-defensins are likely to constitute the essential primary structural motif of this ancient family of host-defense peptides.

Amino Acid Sequence↗
PubMed1994

Rates and outcomes of diabetic end-stage renal disease among registered native people in Saskatchewan.

OBJECTIVE: To determine the rates and outcomes of diabetic end-stage renal disease (ESRD) among registered native people and non-native people in Saskatchewan. DESIGN: Retrospective population-based study using data from the Canadian Organ Replacement Registry. SETTING: Saskatchewan. PATIENTS: All patients with diabetic ESRD diagnosed between Jan. 1, 1981, and Dec. 31, 1990. MAIN OUTCOME MEASURES: Incidence rates of diabetic ESRD in the general population, rates of diabetic ESRD among patients with diabetes mellitus, nature of initial dialysis treatment, length of survival from start of dialysis, cause of death and renal transplant rates. RESULTS: The 10-year incidence rates of diabetic ESRD were higher among all age groups among registered native people than among non-native people. The overall relative risk ratio for native people was 16.2. When a higher prevalence of diabetes among native people was taken into account, native diabetic people were still seven times as likely as non-native diabetic people to manifest diabetic ESRD. The median survival from start of dialysis was under 2 years in both groups, but more native people died of stroke and more non-native people died of heart disease. Non-native diabetic people were more likely than native diabetic people to receive renal transplants. CONCLUSIONS: Although the overall incidence of diabetic ESRD in Saskatchewan is increasing, registered native people have a disproportionate risk for this serious complication.

Adult↗
PubMed1994

Association of abnormalities of chromosome 11 with t(14;18) in diffuse non-Hodgkin's lymphoma.

Cytogenetic studies of non-Hodgkin's lymphomas (NHL) have revealed a nonrandom translocation, t(14;18)(q32;q21), to be strongly correlated with follicular histology. In our recent study of 149 cases of NHL, 68 cases had a t(14;18). Forty-four of these were follicular and 24 diffuse. In the majority of cases (90%) there were additional chromosome abnormalities, which were analyzed to determine whether any were specifically associated with diffuse histology. Chromosome 11 abnormalities occurring together with the t(14;18) were found to be present in 17/68 cases; 14/17 (82%) were diffuse and 3/17 (18%) were follicular NHL. Thus, 14/24 (58%) of all diffuse lymphomas with t(14;18) had an abnormality of chromosome 11 compared to only 3/44 (7%) of follicular lymphomas, suggesting that the addition of an abnormality of chromosome 11 to a t(14;18) karyotype is associated with diffuse histology.

Adult↗
PubMed1994

Proliferating cell nuclear antigen expression in the survival of astrocytoma patients.

The PC10, a monoclonal antibody against proliferating cell nuclear antigen (PCNA), is known to show immunoreactivity in routinely processed paraffin embedded tissue. This antibody was applied to 72 astrocytic tumours from surgical biopsy material obtained in a ten year period. The PCNA labelling index (LI) obtained by image analysis was compared with patient's survival, age at diagnosis, and Karnofsky score as well as the histological grade of tumour. The survival analysis shows that patients with tumour PCNA LI of more than 6% have significantly poorer prognosis than those with 6% and below. In addition, there is also good correlation between PCNA LI with age, Karnofsky and tumour grade. This study suggests that although the PCNA expression of astrocytoma could be a useful predictor of patient's outcome, it is not an independent prognostic factor but has derived its statistical association with survival secondarily through its relationship with tumour grade, age and Karnofsky score.

Adolescent↗
PubMed1994

Radiotherapy in the treatment of malignant mesothelioma of the pleura, with special reference to its use in palliation.

Most patients presenting with malignant mesothelioma of the pleura (MMP) are only suitable for palliative treatment. Radiotherapy has not been shown to improve survival in patients with this disease, but is of use in the palliation of symptoms. In this retrospective review of 111 patients with MMP referred to the Peter MacCallum Cancer Institute, the palliative effect of radiotherapy was analysed. More than half of the patients whose response could be assessed had some symptomatic relief from the radiotherapy treatment. No dose-response relationship could be found.

Adult↗
PubMed1994

Middle ear mucosal inflammation: an in vivo model.

The inflammatory process underlies the pathogenesis of otitis media (OM). Although knowledge concerning this common childhood disease continues to accumulate, most of the basic science research is based on in vitro or ex vivo methodologies. Magnetic resonance imaging (MRI), although lauded for its ability to image soft tissue, is often neglected as a research tool providing real-time in vivo information. This study attempts to assess experimental middle ear (ME) inflammation using MRI. The vasoactive effects of histamine and its interaction with antihistamines and a glucocorticoid were evaluated. Histamine was chosen because it is one of the naturally occurring inflammatory mediators. The antagonists were selected on the basis of their antihistaminic and vasoactive effects, respectively. Certainly there is substantial clinical interest in these agents because their efficacy for the treatment of OM is still being debated. The chinchilla model was chosen since it is one of the best characterized species in the study of OM. The three parts of the study are as follows: the effects of histamine on chinchilla ME mucosa; histamine challenge following pretreatment using hydroxyzine hydrochloride (H1 antagonist), ranitidine chloride (H2 antagonist), and the combination; and histamine challenge following pretreatment with dexamethasone. Sequential T1-weighted spin-echo (SE) MRI was used to detect extravasation of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) into the middle ear effusion (MEE). The results indicate that the vasoactive effects of histamine are dose-related and can be assessed across a wide spectrum of histamine dosages inclusive of the human MEE levels. The H1 antagonist alone, or in combination with the H2 antagonist, was able to prevent the increased vascular permeability induced by histamine. When used alone, the H2 antagonist did not abolish the effects of histamine. The vasoactive effects of histamine were also ameliorated by pretreatment with a glucocorticoid. These findings indicate the utility of MRI for assessing mucosal inflammation in a real-time manner rather than as an accumulation of events. This study also validates the efficacy of an H1 antagonist and a glucocorticoid in counteracting the vasoactive effects of histamine. This methodology may be suited for evaluating the effects of other classes of antiinflammatory mediators.

Animals↗
PubMed1994

Peripheral blood lymphocyte surface antigen expression and prognosis in myeloma: Australian Leukaemia Study Group Study.

The Australian Leukaemia Study Group myeloma study (MM1) aimed to determine the prognostic significance of clinical and immunophenotypic markers in patients with multiple myeloma. All patients were treated with standard dose melphalan and prednisone. Seventy-four patients were entered and the median survival was 27 months. Serum beta 2-microglobulin (beta 2M) and albumin levels were the only significant clinical factors influencing survival (p = 0.007 and p = 0.008, respectively). Patients with raised levels of CD38+ lymphocytes at presentation had a significantly shorter survival than patients with normal levels (p = 0.01, logrank test, median 19 months vs 33 months). CD38 antigen expression was independent of beta 2M but patients with raised levels of CD38 had significantly lower levels of albumin than patients with normal levels (p = 0.001) which may explain their poorer survival. Salmon and Durie stage was not associated with antigen expression. No other B-cell antigens (CD10, CD19, CD20, CD21, CD22, CD23, FMC1 or FMC7) or plasma cell antigens tested (PCA-1) were found to be associated with prognosis. Patients who achieved plateau phase had a better prognosis than those who did not (p = 0.04 in a landmark analysis). Patients who achieved plateau phase following an objective response appeared to have a better prognosis than those who were in plateau phase at presentation (p = 0.09 in a landmark analysis). Light chain isotype suppression (LCIS) was not associated with a significant survival advantage and did not correlate with any known prognostic indicator.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

[The effect of acupuncture on the function of macrophages in rats of immunodepression].

The immunodepression model was established by means of intraperitoneal injection of cyclophosphamide in rats. Their phagocytic percentage and phagocytic index of peritoneal macrophages (PM phi) as well as serum lysozyme (LSZ) decreased obviously; After 6 days of acupuncture at "Zusanli" points (ST 36), PM phi phagocytic percentage and phagocytic index increased significantly, Serum LSZ showed no significant change. These results indicate that acupuncture can increase the phagocytic function of M phi in rats of immunodepression, but Serum LSZ level does not synchronously increase with the phagocytic function of M phi.

Acupuncture Therapy↗
PubMed1994

Glomerular expression of monocyte chemoattractant protein-1 in experimental and human glomerulonephritis.

BACKGROUND: Glomerular monocytes are found in a variety of renal diseases and appear to be important in the pathogenesis of glomerular injury. The mediators responsible for recruiting monocytes to the glomerulus are not well characterized. We have recently established that cultured human mesangial cells produce the specific monocyte chemoattractant, monocyte chemoattractant protein-1 (MCP-1) in response to inflammatory cytokines commonly found in glomeruli during glomerulonephritis (GN). This suggested that MCP-1 may be involved in recruiting leukocytes to the glomerulus. To date however, there is little information regarding the expression of MCP-1 during renal disease. The present study was undertaken to investigate the in vivo expression of MCP-1 during experimental and human GN. EXPERIMENTAL DESIGN: A rodent model of anti-glomerular basement membrane GN was used to investigate glomerular MCP-1 mRNA regulation and protein expression. The presence of MCP-1 in human renal tissue was studied by immunostaining kidney biopsy material from patients with a variety of glomerulopathies. RESULTS: MCP-1 mRNA was transiently upregulated during the early stages of experimental GN. Message levels increased in association with the monocyte influx and correlated with expression of immunoreactive MCP-1 in the nephritic glomeruli. Glomerular MCP-1 was also found in human inflammatory glomerulopathies, but not in glomerular diseases lacking a prominent monocyte infiltrate. CONCLUSIONS: These data support a role for MCP-1 in the pathogenesis of glomerular inflammation.

Animals↗
PubMed1994

Evidence in infants with cleft palate that breast milk protects against otitis media.

OBJECTIVE: Most infants with cleft palate suckle unproductively and require feeding by artificial means. Most also have unremitting otitis media accompanied by (usually) nonpurulent middle-ear effusion, a complication generally attributed to impaired eustachian tube ventilatory function. We observed two infants with cleft palate in whom one or both ears appeared effusion-free on more than one occasion, and who also were receiving or previously had received breast milk feedings. This prompted us to analyze the relation between middle-ear status and feeding mode in a large series of infants with cleft palate. Our objective was to determine whether in these infants the receipt of breast milk mitigated the otherwise virtually invariable development and continued presence of otitis media. METHODS: We reviewed and analyzed data concerning both feeding mode and the presence or absence of middle-ear effusion in 315 infants with cleft palate, as recorded systematically in the course of prospective studies at our Cleft Palate-Craniofacial Center. Analysis was limited to periods preceding the infants' receipt of tympanostomy-tube placement or palate repair, or their second birthday, whichever occurred first. RESULTS: Freedom from effusion in one or both ears was found at one or more visits in only seven (2.7%) of 261 infants fed cow's milk or soy formula exclusively, but in 17 (32%) of 54 infants fed breast milk exclusively or in part for varying periods (P < .0001). In virtually all instances, the breast milk had been harvested by the mother and fed to the infant via an artificial feeder. Baseline clinical and sociodemographic characteristics and surveillance in the two groups of infants were comparable. CONCLUSIONS: Artificially fed breast milk provides variable protection against the development of otitis media in infants with cleft palate. This finding supports the likelihood of a similarly protective effect of breast milk in noncleft infants. The finding also suggests strongly that in infants with cleft palate, impaired eustachian tube function is not the only pathogenetic factor in the infants' initial development of middle-ear effusion.

Breast Feeding↗