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Biomedical subjects

T J Brown

Publications and source records attributed to T J Brown.

At least 37 records · Page 2Linked to original sources
PubMed2001

Neuroprotective effects of gonadal steroids on regenerating peripheral motoneurons.

In this review, the neuroprotective actions of testosterone on three different populations of injured rat peripheral motoneurons, i.e. facial (FMN), spinal (SMN) and pudendal (PMN), will be discussed. We have extrapolated concepts from the neuroendocrine field regarding the trophic effects of gonadal steroids on target neural tissue to the nerve regeneration field. Exogenous administration of testosterone immediately after nerve injury impacts positively on functional recovery through actions mediated by the androgen receptor. The mechanism by which steroidal enhancement of the regenerative properties of injured motoneurons occurs may involve pre-existing androgen receptors, heat shock proteins, and modulation of the cellular stress response.

Animals↗
PubMed2001

Antiviral agents.

The potential severity of many viral infections and the lack of appropriate treatment for these diseases have been a source of endless frustration and helplessness for clinicians. The newly developed field of antiviral therapy is expanding at an astounding rate, with new discoveries each day. Although physicians are not yet able to cure many of the viral infections, such as HSV, HIV, and CMV, a means of controlling them is available. It is hoped that the research and investigations currently under way will lead to a future era of antiviral drugs that will be able to eradicate these diseases.

AIDS-Related Opportunistic Infections↗
PubMed2001

Loss of androgen receptor associated protein 70 (ARA70) expression in a subset of HER2-positive breast cancers.

Co-transfection studies indicate that HER2 (erbB-2) overexpression results in the phosphorylation and enhanced transcriptional activity of the androgen receptor (AR). This amplification of AR action is further enhanced by the expression of ARA70, a putative co-activator with a predilection for the AR. Because androgens inhibit the growth of breast cancer cells whereas HER2 overexpression stimulates the growth of these cells, it seems possible that loss of expression of AR or ARA70 in some HER2 overexpressing tumors might confer a growth advantage to these cells. We examined ARA70 and AR expression in 20 HER2-positive (overexpressing) and 21 HER2-negative cases of breast invasive ductal carcinoma (IDC) to determine the relationship between loss of ARA70 and/or AR with HER2 overexpression. Strong ARA70 immunostaining was observed in all normal and breast epithelial cells in fibrocystic change and in in situ carcinoma present in the patient samples. Of the 41 cases of IDC, focal or complete loss of ARA70 protein expression was observed in 46% of the cases, with 60% of HER2-positive versus 33% of HER2-negative cases showing loss. Loss of AR expression was observed in 60% of HER2-positive versus 43% of HER2-negative cases. Remarkably, only 20% of HER2-positive tumors expressed both AR and ARA70, while 43% of HER2-negative tumors expressed both of these elements of the AR signaling pathway. This trend is consistent with a possible clinical relevance of the potential crosstalk between the HER2 and AR signaling pathways. Western blot analysis for ARA70 expression performed on frozen breast biopsies of normal or malignant breast tissue from four patients revealed a 70 kDa immunoreactive band in all four normal tissue samples, with an additional 35 kDa band in two of the breast cancer samples and in human breast cancer MCF-7 cells. This may reflect aberrant splicing in some breast cancers, leading to the emergence of the 35 kDa isoform.

Biopsy↗
PubMed2001

Perineural invasion of cutaneous malignancies.

BACKGROUND: Perineural invasion is an important mode of tumor spread and is associated with increased aggressiveness and a propensity for recurrence among cutaneous malignancies. OBJECTIVE: To review the pathogenesis, diagnosis, and treatment of cutaneous tumors exhibiting perineural invasion. METHODS: This article is based on a review of the medical literature concerning tumors with perineural involvement. RESULTS: This article describes the clinical signs and histologic features of cutaneous malignancies exhibiting perineural involvement. CONCLUSION: Appropriate patient care mandates consideration of perineural invasion in the evaluation of cutaneous tumors. As the majority of patients present without symptoms of neural involvement, physicians must be vigilant in the search for this type of tumor spread.

Humans↗
PubMed2001

Rifampin resistance in Mycobacterium kansasii is associated with rpoB mutations.

Rifampin is the most potent drug used in the treatment of disease due to Mycobacterium kansasii. A 69-bp fragment of rpoB, the gene that encodes the beta subunit of the bacterial RNA polymerase, was sequenced and found to be identical in five rifampin-susceptible clinical isolates of M. kansasii. This sequence showed 87% homology with the Mycobacterium tuberculosis gene, with an identical deduced amino acid sequence. In contrast, missense mutations were detected in the same fragment amplified from five rifampin-resistant isolates. A rifampin-resistant strain generated in vitro also harbored an rpoB gene missense mutation that was not present in the parent isolate. All mutations detected (in codons 513, 526, and 531) have previously been described in rifampin-resistant M. tuberculosis isolates. Rifampin MICs determined by E-test were <1 mg/liter for all rifampin-susceptible isolates and >256 mg/liter for all rifampin-resistant ones. In addition, four of the five rifampin-resistant isolates were also resistant to rifabutin. We have thus shown a strong association between rpoB gene missense mutations and rifampin resistance in M. kansasii. Although our results are derived from a small number of isolates and confirmation with larger numbers would be useful, they strongly suggest that mutations within rpoB form the molecular basis of rifampin resistance in this species.

Amino Acid Sequence↗
PubMed2001

DNA array technology and diagnostic microbiology.

Near instantaneous detection of pathogens from clinical material, combined with simultaneous prediction of their antimicrobial resistance profiles, would revolutionize the impact of microbiology on the management of infection. Array-based assays allow a range of characteristics to be rapidly and simultaneously determined. At present these systems have found their primary role as research tools for the monitoring of mRNA expression in the form of DNA microarrays or 'chips'. As fabrication costs reduce and validated targeted arrays are developed, it is inevitable they will be used for more routine applications. Microfluidics offers the exciting possibility of combining purification, amplification and detection in a single disposable device; microarrays are particularly suitable for use within these systems. Arrays will become an important tool for clinical diagnostics.

Animals↗
PubMed2001

Androgenic enhancement of betaII-tubulin mRNA in spinal motoneurons following sciatic nerve injury.

PURPOSE: We have previously demonstrated that systemic administration of testosterone propionate (TP) can accelerate the functional recovery from hind limb paralysis following sciatic nerve injury in the rat. In this study, we looked at the molecular mechanisms underlying this phenomenon. METHODS: Castrated adult male rats received a right side sciatic nerve crush at the level of the sciatic notch, with the left side serving as control. Half the animals received a subcutaneous implant of TP, the others were sham implanted. Animals were sacrificed at 1, 3, 7 and 10 days post-operative. Lumbar spinal cord tissue was harvested and in situ hybridization was performed using a cytoskeletal cDNA probe complementary to betaII-tubulin. RESULTS: On the injured side, sciatic motoneuron tubulin mRNA levels were increased in alt groups at alt time points. At 3 and 7 days post- op, the TP treated group had significantly higher levels of tubulin mRNA. CONCLUSIONS: These results suggest that testosterone enhances the rate of regeneration by increasing the neuronal cytoskeletal response after axonal injury. Further, these results, coupled with the results from previous experiments in other rodent models, suggest a common mechanism for gonadal steroid action on regenerating motoneurons across species.

Animals↗
PubMed2000

Studies of isopenicillin N synthase enzymatic properties using a continuous spectrophotometric assay.

Isopenicillin N synthase (IPNS) from Aspergillus nidulans is a no-heme iron(II)-dependent oxygenase which catalyses, in a single reaction, the bicyclisation of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine into isopenicillin N, the precursor of all other penicillins, cephalosporins and cephamycins. The IPNS reaction can be followed directly and continuously by a new assay which monitors the absorbance increase at 235 nm characteristic of penicillin nucleus formation. Using this assay, the effects of influential factors affecting the in vitro IPNS enzymatic reaction were investigated. Even under optimal conditions, enzyme inactivation occurred during catalysis. Iron(II) depletion and product inhibition were not the cause of this phenomenon, the addition of antioxidants or reducing agents failed to slow down inactivation or reactivate the enzyme. Therefore, this phenomenon appears to be irreversible and is attributed to oxidative damage caused to the enzyme by reactive oxygen species generated in solution during catalysis. Nevertheless, the steady-state kinetic parameters for the IPNS reaction were determined.

Antioxidants↗
PubMed2000

Prevalence and strain differentiation of Giardia intestinalis in calves in the Manawatu and Waikato regions of North Island, New Zealand.

Giardia intestinalis has been reported in newborn calves world-wide; however, information on the extent of G. intestinalis in New Zealand calves has to date been very limited. The current study attempted to establish the prevalence rate of G. intestinalis in calves up to 8 weeks old in New Zealand. More than 700 calf fecal specimens were collected during the spring calving seasons of 1998 and 1999 from two regions in North Island, New Zealand (Manawatu and Waikato) and tested for the presence of G. intestinalis. In addition to determining the presence of G. intestinalis in newborn calves, sequence analysis was performed using specific amplification primers developed to target a section of the ribosomal DNA (rDNA). This locus is considered to be rapidly evolving, and therefore, suitable for use in the elucidation of phylogenetic relationships between G. intestinalis isolates. Sequencing was performed using G. intestinalis DNA extracted from cysts collected directly from the calf fecal matter. There was no culturing of the G. intestinalis isolates either in vivo or in vitro. Over 40% of all collected calf fecal specimens contained G. intestinalis cysts and rDNA sequence analysis revealed two different sequences among calf isolates. These sequence differences were not found to correspond to a particular season, geographical region or farming practice. Preliminary phylogenetic analysis suggests that these two rDNA sequence types are indicative of calf hosts.

Animals↗
PubMed2000

Selective ET(A) antagonists. 5. Discovery and structure-activity relationships of phenoxyphenylacetic acid derivatives.

The fifth paper in this series describes the culmination of our investigations into the development of a potent and selective ET(A) receptor antagonist for the treatment of diseases mediated by ET-1. Receptor site mapping of several ET(A) antagonists prepared previously identified a common cationic binding site which prompted synthesis of phenoxyphenylacetic acid derivative 13a, which showed good in vitro activity (IC(50) 59 nM, rat aortic ET(A)). Optimization of 13a led to the identification of 27b, which exhibited an IC(50) of 4 nM. Although this did not translate into the expected in vivo potency, a compound of comparable in vitro activity, 27a (RPR118031A), showed a far better pharmacokinetic profile and in vivo potency (75 micromol/kg) and was duly proposed and accepted as a development candidate.

Administration, Oral↗
PubMed2000

Down-regulation of transforming growth factor beta receptors by androgen in ovarian cancer cells.

Steroid hormones have been implicated in the etiology and/or progression of epithelial ovarian cancer. As ovarian surface epithelial cells are growth inhibited by transforming growth factor beta (TGF-beta), we tested whether steroid hormones could regulate the expression of TGF-beta1 or its receptors in ovarian cancer cells, as assessed by quantitative reverse transcription-PCR. Treatment of ovarian cancer HEY cells with 500 nM 5alpha-dihydrotestosterone (DHT), but not estradiol-17beta or progesterone, for 60 h down-regulated the expression of mRNA for TGF-beta receptors I and II (TbetaR-I and TbetaR-II), betaglycan, and endoglin but had no effect on TGF-beta1 mRNA levels. Androgen receptor (AR) mRNA expression in HEY cells was compared to other ovarian cancer cell lines. OVCAR-3 cells expressed AR mRNA levels similar to that of androgen-responsive LNCaP prostate cancer cells, whereas SKOV-3 and HEY cells expressed only 3 and 0.01%, respectively. Western blot analysis and saturation binding assays confirmed the expression of AR protein in these three cell lines, but at the limit of detection in SKOV-3 and HEY cells. Treatment of SKOV-3 and HEY cells for 24 h with 1-50 nM DHT resulted in a dose-dependent down-regulation of TbetaR-II mRNA. The AR antagonist hydroxyflutamide did not reverse the effect of DHT on SKOV-3 cells but by itself down-regulated TbetaR-II mRNA. This apparent androgen-mimetic action of hydroxyflutamide and the ability of SKOV-3 and HEY cells to respond to DHT may be due to their expression of AR-associating protein 70, an AR co-activator reported to amplify AR transactivation and to result in agonist activity of AR antagonists. DHT was able to reverse TGF-beta1 growth-inhibitory action in SKOV-3 cells and in a primary culture of ovarian cancer cells derived from ascites. Thus, androgens may promote ovarian cancer progression in part by decreasing TGF-beta receptor levels, thereby allowing ovarian cancer cells to escape TGF-beta1 growth inhibition.

Dihydrotestosterone↗
PubMed2000

A new disorder of hyaluronan metabolism associated with generalized folding and thickening of the skin.

OBJECTIVE: To describe and characterize a new disorder of hyaluronan metabolism associated with marked abnormalities of cutaneous tissue and to determine whether a relationship with a phenotypically similar disorder in the shar-pei dog exists. METHODS: Biopsy specimens of the skin of a child with extreme cutaneous thickening and folding were examined by light and electron microscopy. The concentration of hyaluronan and the activity of hyaluronidase were measured in the patient's serum and plasma, respectively, and the activity of hyaluronan synthase was examined in cultured dermal fibroblasts. Hyaluronan concentration was also measured in the plasma of 23 shar-pei and 34 control dogs. RESULTS: The patient's skin displayed gross accumulation of hyaluronan, and the serum concentration of hyaluronan was markedly elevated (up to 3100 microg/L) during infancy. Hyaluronan synthase activity of cultured dermal fibroblasts was increased, whereas hyaluronidase activity in plasma was normal (5.5 +/- 0.08 IU/L). Plasma hyaluronan concentration was higher in the shar-pei dogs than in control dogs (median, 378 microg/L vs 73 microg/L, respectively). CONCLUSION: The child we describe has a novel disorder of hyaluronan metabolism, which appears to result from abnormal control of hyaluronan synthesis. An analogous disorder may be present in the shar-pei dog.

Animals↗
PubMed2000

The addition of low numbers of 3' thymine bases can be used to improve the hybridization signal of oligonucleotides for use within arrays on nylon supports.

Oligonucleotide arrays can be used for the analysis of microbial nucleic acid. The addition of high numbers of dTTP to the 3' ends of oligonucleotides using terminal transferase has been shown to facilitate membrane binding. This paper demonstrates low numbers of thymine bases added to the 3' end of oligonucleotides during synthesis can improve hybridisation signal intensity where the signal seen with the unmodified oligonucleotides is poor. Thus, the addition of variable numbers of thymine bases to different oligonucleotides allows the production of oligonucleotide arrays producing strong interpretable hybridisation signals.

Antibiotics, Antitubercular↗
PubMed2000

Biosynthesis of glycosaminoglycans and proteoglycans by the lymph node.

Previous studies of hyaluronan uptake and catabolism by lymph nodes indicated that the nodes might also add some HA of low molecular weight to the unabsorbed fraction that passes through from afferent to efferent lymph vessels. The ability of lymph nodes to synthesise HA and proteoglycans was therefore examined (i) by perfusion of [(3)H] acetate through an afferent lymph vessel in vivo, and recovery of labeled products from the efferent lymph vessel and from the node after perfusion; and (ii) by tissue culture of lymph nodes with [(3)H] acetate. Perfusion of lymph nodes with [(3)H] acetate in situ yielded: (a), in outflowing lymph, small amounts of chondroitin/dermatan sulfate within the first hour which continued to be produced for up to 24 h; heparin in the second hour and HA in the third. In the nodes removed 17 to 19 h later, equal amounts of hyaluronan and chondroitin/dermatan sulfate and heparan sulfate proteoglycans were detected. In the tissue culture of lymph nodes: (1) HA, heparin and proteoglycans of heparan sulfate and chondroitin/dermatan sulfate were released into the medium but in the cell extract only heparan sulfate proteoglycan was detected; and (ii) molecular weight of the released hyaluronan ranged widely but was mostly less than 4-5x10(5)D; heparan sulfate proteoglycan was 2.8x10(4) to 9.4x10(5)D; heparin 7.9x10(4)D and chondroitin sulfate 1.3x10(4)D, suggesting that the chondrotin sulfate were released from their proteoglycans core by enzymic degradation. It is concluded that lymph nodes can release HA, heparin, heparan sulfate and chondroitin/dermatan sulfate proteoglycans into efferent lymph but the amount of hyaluronan is likely to be small without immune or other stimulation and its molecular weight is lower than in other tissues.

Acetates↗
PubMed2000

Complete spontaneous regression of Merkel cell carcinoma: a review of the 10 reported cases.

BACKGROUND: Merkel cell (neuroendocrine) carcinoma (MCC) is a very aggressive primary cutaneous neoplasm occurring most often on the head and neck of the elderly. Complete spontaneous regression (CSR) of MCC was first described in 1986. Since then other cases have been reported bringing the total to 10. OBJECTIVE: To review these 10 cases and obtain long-term follow-up data, to compare them for similarities and differences. METHOD: Each original case report was extensively reviewed and authors contacted in most cases for confirmation and updated information. RESULTS: In no case did MCC recur after CSR was noted, although follow-up information in some cases was short. When CSR occurred, it was swift and dramatic with complete regression of skin and lymph node metastasis in 1-3 months. CONCLUSION: While only 10 cases of CSR is a small number, MCC is itself a rare malignancy with just over 600 reported cases. Today most cases of MCC receive aggressive combined therapy effectively precluding diagnosis of CSR. The nature of regression in these 10 cases may point toward future immunologic therapy just as similar cases of CRS in patients with melanoma have led to advances in the immunologic treatment for that malignancy.

Aged↗
PubMed2000

Simultaneous identification and typing of multi-drug-resistant Mycobacterium tuberculosis isolates by analysis of pncA and rpoB.

In Mycobacterium tuberculosis there is a strong correlation between in-vitro resistance to rifampicin (RIF) and pyrazinamide (PZA) and mutations in rpoB and pncA, respectively. Approximately 50 mutations associated with resistance have been reported for rpoB and 70 for pncA, and, theoretically, many more are possible. Therefore, the identification of rpoB and pncA mutations in M. tuberculosis might be used for the simultaneous determination of resistance and for typing multi-drug-resistant (MDR) strains during possible outbreaks. The present study examined four sensitive and six MDR isolates of M. tuberculosis from Turkey and eight isolates from a nosocomial MDR tuberculosis (TB) outbreak in the UK. Gene mutations were identified by the Innogenetics LiPA rpoB assay or automated sequencing, or both. All the sensitive isolates had rpoB and pncA wild-type genotypes, whereas all the RIF- and PZA-resistant isolates had rpoB and pncA mutations. All four mutations seen in rpoB, but none of the six in pncA, had been reported previously. The rpoB and pncA mutations seen in the Turkish isolates defined six distinct genotypes amongst the six MDR isolates, while standard IS6110 typing discriminated only four. All isolates from the single strain MDR-TB outbreak had identical genotypes. Rapid genotyping was performed on the sputum from a patient who presented 2 years after the initial MDR-TB outbreak and this showed rpoB and pncA genotypes identical to the other outbreak isolates. This result was available within 36 h. The analysis of rpoB and pncA is a rapid and practical means of simultaneously identifying and typing MDR isolates of M. tuberculosis.

Amidohydrolases↗
PubMed2000

Rapid diagnosis of bacteremia by universal amplification of 23S ribosomal DNA followed by hybridization to an oligonucleotide array.

The rapid identification of bacteria in blood cultures and other clinical specimens is important for patient management and antimicrobial therapy. We describe a rapid (<4 h) detection and identification system that uses universal PCR primers to amplify a variable region of bacterial 23S ribosomal DNA, followed by reverse hybridization of the products to a panel of oligonucleotides. This procedure was successful in discriminating a range of bacteria in pure cultures. When this procedure was applied directly to 158 unselected positive blood culture broths on the day when growth was detected, 125 (79.7%) were correctly identified, including 4 with mixed cultures. Nine (7.2%) yielded bacteria for which no oligonucleotide targets were present in the oligonucleotide panel, and 16 culture-positive broths (10.3%) produced no PCR product. In seven of the remaining eight broths, streptococci were identified but not subsequently grown, and one isolate of Staphylococcus aureus was misidentified as a coagulase-negative staphylococcus. The accuracy, range, and discriminatory power of the assay can be continually extended by adding further oligonucleotides to the panel without significantly increasing complexity or cost.

Bacteremia↗