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Biomedical subjects

J Peters

Publications and source records attributed to J Peters.

At least 253 records · Page 14Linked to original sources
PubMed1997

Tumor suppressor activity of neural cell adhesion molecule in colon carcinoma.

BACKGROUND AND AIMS: Neural Cell Adhesion Molecule (NCAM) is a well-characterized member of the immunoglobin superfamily. The structure of NCAM is similar to the tumor suppressor Deleted in Colon Carcinoma (DCC). NCAM has been found in some epithelial tissues and plays a role in tumorigenesis of some cancers. The purpose of the present study was to determine if NCAM is present in normal human colon. Once its presence was established, its function as a tumor suppressor was investigated. METHODS: Colon tumors and normal proximal margins were processed for reverse transcription-polymerase chain reaction (RT-PCR) of the NCAM-180 message. Immunohistochemistry of the tissue was performed to determine the distribution of NCAM. RESULTS: RT-PCR analysis demonstrated the presence of the NCAM-180 kD isoform in normal colonic epithelia. Immunohistochemistry showed NCAM on the basolateral surface of colonic epithelial cells of the villous tips. Tumors from 15 patients followed up for 4 years were studied. All seven tumors expressing NCAM-180 were from patients having a benign clinical course. Seven of eight tumors that lacked NCAM-180 were associated with aggressive clinical behaviors (presenting with obstruction, perforation or metastatic disease, or patient death within 18 months of presentation). The sole exception was in a villous adenoma excised from a patient who has had multiply recurrent polyps on follow-up. CONCLUSION: We conclude that like DCC, NCAM is an important colonic adhesion molecule that functions as a tumor suppressor.

Adenocarcinoma↗
PubMed1997

Incidence of neurologic complications related to thoracic epidural catheterization.

BACKGROUND: Due to potential neurologic sequelae, the risk:benefit ratio of thoracic epidural analgesia is controversial. Surprisingly, however, few available data address neurologic complications. The incidence of neurologic complications occurring after thoracic epidural catheterization was studied in patients scheduled for abdominal or abdominothoracic surgery. METHODS: A total of 4,185 patients were studied, including 2,059 during the prospective phase of the study and 2,126 during the retrospective phase. After thoracic epidural catheterization, all patients received general anesthesia. Patients' neurologic status was assessed by an anesthesiologist using clinical criteria after operation and after epidural catheter removal. If neurologic complications were suspected, a neurologist was consulted. The incidence of specific complications was compared for different thoracic puncture sites: upper (T3/4-6/7), mid (T7/8-8/9), and lower (T9/10-11/12) catheter insertion levels. RESULTS: The overall incidence of complications after thoracic epidural catheterization was 3.1% (n = 128). This included dural perforation (0.7%; n = 30); unsuccessful catheter placement (1.1%; n = 45); postoperative radicular type pain (0.2%; n = 9), responsive to catheter withdrawal in all cases; and peripheral nerve lesions (0.6%; n = 24), 0.3% (n = 14) of which were peroneal nerve palsies probably related to surgical positioning or other transient peripheral nerve lesions (0.2%; n = 10). No signs suggesting epidural hematoma were recognized, and there were no permanent sensory or motor defects attributable to epidural catheterization. Unintentional dural perforation was observed significantly more often in the lower (3.4%) than in the mid (0.9%), or upper (0.4%) thoracic region. A single patient experienced severe respiratory depression after receiving epidural buprenorphine but recovered without sequelae. CONCLUSIONS: Thoracic epidural catheterization for abdominal and thoracoabdominal surgery is not associated with a high incidence of serious neurologic complications. In fact, the incidence of puncture- and catheter-related complications is less in the mid and upper than in lower thoracic region, and the predicted maximum risk for permanent neurologic complications (upper bound of the 95% confidence interval) is 0.07%.

Analgesia, Epidural↗
PubMed1997

From laboratory to clinic: a large scale study of distortion product otoacoustic emissions in ears with normal hearing and ears with hearing loss.

OBJECTIVES: 1) To describe distortion product otoacoustic emission (DPOAE) measurements in large groups of subjects with normal hearing and with hearing loss, and to use these data to provide comprehensive descriptions of DPOAE test performance. 2) To describe the effects of primary frequency and audiometric threshold on the extent to which DPOAE measurements accurately identify auditory status. 3) To develop an approach that describes the probability that any measured response is coming from either a normal or an impaired ear. 4) To develop an approach for representing DPOAE data clinically. 5) To explore the relation between magnitude of hearing loss and DPOAE measurements. DESIGN: DPOAE measurements were made in 1267 ears of 806 subjects, using stimulus conditions that previously had been demonstrated to result in the greatest separation between normal and impaired ears (i.e., primary levels of 65/55 dB SPL for f1/f2; Stover et al., 1996). Subjects were recruited from local clinical populations and through local advertisements. All data were analyzed using clinical decision theory, including relative operating characteristic (ROC) curves and estimates of areas under these curves (Az). In addition, cumulative distributions were constructed of response properties from both normal and hearing-impaired ears. These cumulative distributions were used to select specific probabilities that measured responses were coming from either the normal or impaired distributions, and to develop an approach for describing clinical DPOAE data. RESULTS: For no conditions were the distributions of DPOAE responses from normal and impaired ears completely separated, meaning that optimal criterion values would still result in errors in identification of auditory status. Test performance, defined by Az, was best for mid and high frequencies and poorest for lower frequencies and for the highest frequency tested (8000 Hz). Performance was best when normal hearing was defined as audiometric thresholds between 20 and 30 dB HL, with poorer performance for more stringent or lax audiometric criteria. CONCLUSIONS: Within the limits related to the effects of primary frequency and audiometric criterion, it appears that DPOAE measurements can be used to accurately identify auditory status. An approach is described, using the present data set, that allows one to assign to any measured DPOAE value (DPOAE amplitudes, DPOAE/noise) the probability that the response is coming either from the distribution of normal or impaired responses. In addition, DPOAE/noise systematically decreases as hearing loss increases over the range of hearing losses from 0 to about 40 to 60 dB HL (depending on frequency), thus potentially enabling one to differentiate hearing losses over this range. For hearing losses greater than 50 to 60 dB HL, ears do not produce measurable DPOAEs and thus, no predictive relationship exists.

Acoustic Stimulation↗
PubMed1997

A comprehensive study of smoking in primary school children in Hong Kong: implications for prevention.

STUDY OBJECTIVE: To identify factors associated with smoking behaviour in primary school children in Hong Kong. DESIGN: A cross sectional survey in which both children and parents completed questionnaires. The main outcome measure was the smoking status of the children; and risk factors (knowledge of and attitude to smoking and demographic and socioeconomic background) were identified as predictors of ever/never smoking. SETTING AND SUBJECTS: Altogether 9598 primary school children, aged 8-13 years, and attending 27 schools from two districts in Hong Kong participated. MAIN RESULTS: The prevalence of ever-smoking was 12% (1119)-15% (760) in boys and 7% (359) in girls. It ranged from 3% in 8 year old girls to 52% in 13 year old boys. The factors associated with ever-smoking included the following: being a boy (adjusted odds ratio 2.21; 95% confidence interval 1.89, 2.59), increasing age per year (1.48; 1.40, 1.57), living in Kwai Tsing district (1.29; 1.10, 1.50), having one or more smokers at home (2.07; 1.78, 2.39), and having a father who was not working (1.41; 1.19, 1.67). Children who were ever-smokers had both seen and approved of their friends' smoking (8.79; 5.33, 14.50), had a more positive attitude towards smoking (3.35; 2.21, 5.09), and were more successful in recognising cigarette brand names and logos (1.67; 1.42, 1.96), but they lacked confidence (1.78; 1.32, 2.39). CONCLUSIONS: The influences on child smoking are multifactorial and programmes in Hong Kong are falling to curb them. The control of these risk factors must be incorporated in the smoking prevention policy of Hong Kong and supported by future enforced legislation.

Adolescent↗
PubMed1997

Detection of rare RNA sequences by single-enzyme in situ reverse transcription-polymerase chain reaction. High-resolution analyses of interleukin-6 mRNA in paraffin sections of lymph nodes.

To study the distribution pattern of interleukin-6 (IL-6)-producing cells in normal human lymph nodes, we applied the in situ reverse transcription-polymerase chain reaction technique. We describe a new modification of this technique for monitoring small amounts of specific nucleotide sequences in conventional paraffin sections. This technique differs in at least two respects from those described earlier. The two decisive steps are: 1) the reverse transcription of mRNA and the subsequent amplification of cDNA by polymerase chain reaction are performed by a new single enzyme capable of both reaction types in one and the same medium without buffer exchange; and 2) for the specific detection of the amplified cDNA, a modified version of the primed in situ labeling technique was used. The technique, carried out on normal human lymph nodes, traces a low load of IL-6 mRNA in fibroblasts, endothelial cells, and a minor population of T lymphocytes in the pulp region. High levels of expression were encountered in about 20% of perisinusoidal pulp macrophages. In addition, moderate activity was detectable in sinus lining cells. Because no major activity was found in the germinal centers of the lymphoid B follicles and in the T zone, it is suggested that the plasma cell differentiation ensuing from primary and secondary B-cell immunization is mainly effected by the sinus lining cells as well as perifollicular and perisinusoidal pulp macrophages capable of producing high amounts of IL-6.

Humans↗
PubMed1997

[Suitability of Bacillus subtilis and Bacillus stearothermophilus spores as test organism bioindicators for detecting superheating of steam].

Biological indicators used to test sterilisation procedures for their efficacy consist of a so-called germ carrier to which the microorganisms used as test organisms adhere. In previous papers we demonstrated that carriers made of filter paper on contact with saturated steam show superheating while carriers made of glass fibre fleece as well as wetted filter paper do not. Using spores of Bacillus subtilis and Bacillus stearothermophilus as test organisms we have now investigated whether and to what extent carrier superheating affects the characteristic values (t50%) of these biological indicators. The indicators were exposed to saturated steam at 100 degrees C (B. subtilis) or 120 degrees C (B. stearothermophilus) under three different exposure conditions: 1. dry (i.e. conditioned to 45% relative humidity before introduction into the sterilising chamber), freely accessible; 2. dry with a substratum and a cover of filter card-board; 3. wet (moistened with twice distilled water before introduction into the sterilising chamber), freely accessible. For previously selected exposure periods, the incidence of indicators with surviving test organisms was determined. The reaction pattern of bioindicators with spores of B. stearothermophilus was different from that of bioindicators with spores of B. subtilis. For B. subtilis, the incidence of bioindicators exhibiting surviving test organisms depended on the nature of the carries as well as on the exposure conditions. On filter paper carriers, t50% increased in the order "wet, freely accessible", "dry, freely accessible", "dry, between filter card-board". On dry and wetted glass fibre fleece, resistance was approximately the same; when the indicators were sandwiched between layers of filter card-board, t50% increased. For B. stearothermophilus, t50% was largely dependent on the carrier material alone. The values obtained for filter paper were invariably much lower than those for glass fibre fleece. As the results show, using spores of B. subtilis it is possible to detect superheating, but the steam resistance of the spores is relatively low. Spores of B. stearothermophilus are of high steam resistance but they are practically unsuitable for detecting superheating. It is imperative to search for a test organism the resistance of which against steam is sufficiently high and which at the same time is capable of reacting to superheating (equivalent to reduced humidity) by a sufficiently large increase in resistance.

Bacillus subtilis↗
PubMed1997

[The dromedary: ancestry, history of domestication and medical treatment in early historic times].

Research on camel bones from archaeological excavations in North Africa and the Near East contradict the current opinion in textbooks that the dromedary and the Bactrian camel are domesticated forms derived from a single species, the two-humped wild camel (C. ferus). The probable ancestor of the domestic one-humped camel is Thomas' camel (C. thomasi). The wild dromedary was probably domesticated on the Arabian peninsula, perhaps as early as the 4th millennium BC. From the 2nd millennium BC onward there is evidence for the use of the one-humped camel for riding and transport purposes. Camel-keeping also implied the therapy of diseased animals, the main source of information about their treatment being medieval arabic texts dealing with veterinary medicine. An expert of such an early 13th century text is presented and discussed. From this it can be seen that the medieval camel treatment fits the principles of the so-called humoral theory, a medical concept which at that time already existed for more than 1500 years.

Africa, Northern↗
PubMed1996

Glomerular-specific imprinting of the mouse gsalpha gene: how does this relate to hormone resistance in albright hereditary osteodystrophy?

The gene for alpha-stimulating guanine-nucleotide binding polypeptide, Gnas, has been considered as a candidate for the imprinting effects ascribed to distal mouse Chromosome (Chr) 2. Its human homologue (GNAS1) appears, from clinical and biochemical studies of patients with Albright hereditary osteodystrophy, to be paternally imprinted. GNAS1 maps to 20q13, a region that shows linkage conservation with distal mouse Chr 2. We have mapped Gnas within the imprinting region on distal Chr 2 by linkage analysis. To establish if Gnas is imprinted, we have looked for expression differences in tissues taken from mice carrying maternal duplication/paternal deficiency for distal Chr 2 (MatDp2) and its reciprocal (PatDp2). RNA in situ hybridization revealed high levels of Gnas mRNA in glomeruli of PatDp2 embryos at late gestation and lower levels in glomeruli of MatDp2 embryos. These results strongly suggest that Gnas is maternally imprinted and suggest that the mouse gene may be imprinted in a manner opposite that predicted in human.

Alleles↗
PubMed1996

A hyperthermostable protease of the subtilisin family bound to the surface layer of the archaeon Staphylothermus marinus.

BACKGROUND: Staphylothermus marinus, an archaeon isolated from a geothermally heated marine environment, is a peptide-fermenting, sulphur-dependent organism with an optimum growth temperature of 92 degrees C. It forms grapes of cells, which adhere to each other and to sulphur granules via their surface layer. This glycoprotein layer forms a canopy which is held at a distance of about 70 nm from the cell membrane by membrane-anchored stalks, thereby enclosing a 'quasi-periplasmic space'. Two copies of a globular protease, which probably serves an exodigestive function related to the organism's energy metabolism, are attached near the middle of each stalk. RESULTS: We have purified and characterized this protease with regard to its enzymatic properties and thermostability, and have sequenced its gene using an approach based entirely on the polymerase chain reaction. The precursor form is 1345 amino acids long; between residues 64-741, it contains a domain with clear homology to subtilisins, which is interrupted by two large insertions. The enzyme has a broad substrate specificity and a pH optimum of 9.0. It is fully stable from pH 3.2 to 12.7 and is resistant to heat-inactivation to 95 degrees C in the free form and to 125 degrees C in the stalk-bound form. CONCLUSIONS: This protease is one of the most stable proteases known. Its high resistance towards denaturing agents makes it an interesting target for practical applications. Despite its large size, it is clearly a member of the subtilisin family and represents the only known enzyme that is a stoichiometric S-layer component.

Amino Acid Sequence↗
PubMed1996

Hyperthermostable surface layer protein tetrabrachion from the archaebacterium Staphylothermus marinus: evidence for the presence of a right-handed coiled coil derived from the primary structure.

The scaffold of the surface layer covering the hyperthermophilic archaebacterium Staphylothermus marinus is formed by an extended filiform glycoprotein complex, tetrabrachion, which is anchored in the cell membrane at one end of a 70 nm stalk and branches at the other end into four arms of 24 nm length. The arms from a canopy-like meshwork by end-to-end contacts, enclosing a "quasi-periplasmic space". The primary structure of the complex, obtained by an approach based entirely on the polymerase chain reaction, shows that the light and the heavy chains are encoded in this order in a single gene and are generated by internal proteolytic cleavage. One light chain associates with the N-terminal part of a heavy chain to form one of the four arms of the complex, comprising about 1000 residues. Following a glycine-rich linker of about ten residues, the C-terminal 500 residues of the four heavy chains converge to form a four-stranded parallel coiled coil, which ends in a transmembrane segment. The sequence of the coiled coil is exceptional in that the heptad repeat of hydrophobic residues typical for left-handed coiled coils shifts to an undecad repeat after an internal proline residue, indicating that the C-terminal part of the sequence forms a right-handed coiled coil. Such a periodicity has not been detected in coiled coils to date. The almost flawless pattern of aliphatic residues, mainly leucine and isoleucine, throughout the hydrophobic core of the stalk provide one explanation for its exceptional stability.

Archaea↗
PubMed1996

Acetylcholine as a mitogen: muscarinic receptor-mediated proliferation of rat astrocytes and human astrocytoma cells.

The mitogenic effect of muscarinic receptor agonists in glial cells has been characterized in rat cortical astrocytes and human 132 1N1 astrocytoma cells. The muscarinic receptor agonist carbachol caused a dose- and time-dependent increase in proliferation, as measured by [3H]thymidine incorporation. The mitogenic effect was mimicked by several muscarinic, but not nicotinic receptor agonists, and was blocked by muscarinic receptor antagonists. Reverse transcription-polymerase chain reaction (RT-PCR) experiments indicated the presence of m2, m3 and to a lesser degree, m5 muscarinic receptor mRNA in both astrocytes and astrocytoma cells. Proliferation experiments with subtype-specific muscarinic receptor antagonists suggest that carbachol-induced proliferation is due to activation of muscarinic M3 receptors. The phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA) also stimulated glial cell proliferation. Down-regulation of protein kinase C, or the protein kinase C antagonist 1,5-(isoquinolynsulfanyl)-2-methylpiperazine dihydrochloride (H7) blocked proliferation induced by either TPA or carbachol. Of other neurotransmitters tested, histamine caused glial cell proliferation, norepinephrine and gamma-aminobutyric acid were ineffective, while serotonin and glutamate inhibited basal or serum-stimulated proliferation.

Acetylcholine↗