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Biomedical subjects

J Hall

Publications and source records attributed to J Hall.

At least 307 records · Page 17Linked to original sources
PubMed1992

Bad management, bad business.

The past ten years the market for dentists in Denmark has been shrinking. This is having an effect on the financial position of dental practices. It is more difficult for dentists to maintain a certain income level. Several problems are analysed and possible solutions are being discussed.

Denmark↗
PubMed1992

The impact of multiskilled practice on the job satisfaction of medical laboratory personnel.

This study examined practice patterns of medical laboratory personnel and investigated relationships of job-related variables and job satisfaction for single- and multiskilled practitioners. Data were collected from a random sample of American Society of Clinical Pathologist-registered practitioners in a five-state region. Twenty-five percent of the sample was categorized as multiskilled. Regression analysis revealed that work performed had a significant positive contribution to overall job satisfaction for medical laboratory technicians (MLTs) and medical technologists. The strength of the relationship was weakest for multiskilled MLTs. Results support the contention that when jobs are redesigned, enriching them by adding tasks of increased complexity and challenge is possibly more effective than simply enlarging the jobs with lower- or parallel-level tasks.

Adult↗
PubMed1991

The non-catalytic C-terminal region of endoglucanase E from Clostridium thermocellum contains a cellulose-binding domain.

Mature endoglucanase E (EGE) from Clostridium thermocellum consists of 780 amino acid residues and has an Mr of 84,016. The N-terminal 334 amino acids comprise a functional catalytic domain. Full-length EGE bound to crystalline cellulose (Avicel) but not to xylan. Bound enzyme could be eluted with distilled water. The capacity of truncated derivatives of the enzyme to bind cellulose was investigated. EGE lacking 109 C-terminal residues (EGEd) or a derivative in which residues 367-432 of the mature form of the enzyme had been deleted (EGEb), bound to Avicel, whereas EGEa and EGEc, which lack 416 and 246 C-terminal residues respectively, did not. The specific activity of EGEa, consisting of the N-terminal 364 amino acids, was 4-fold higher than that of the full-length enzyme. The truncated derivative also exhibited lower affinity for the substrate beta-glucan than the full-length enzyme. It is concluded that EGE contains a cellulose-binding domain, located between residues 432 and 671, that is distinct from the active site. The role of this substrate-binding domain is discussed.

Binding Sites↗
PubMed1991

Solution conformation of endothelin, a potent vaso-constricting bicyclic peptide. A combined use of 1H NMR spectroscopy and distance geometry calculations.

The solution structure of endothelin-1, a newly discovered potent bicyclic peptide vaso-constrictor agent, has been investigated using 1H NMR conformational constraints and distance geometry calculations. The conformation is constrained by two disulphide bridges between Cys1-Cys15 and Cys3-Cys11 but the NMR data and computed conformers show additional helical structure between residues Leu6 and Cys11. Our results are compared with previous conflicting reports on the solution conformation of this peptide.

Amino Acid Sequence↗
PubMed1991

MK-801 and ketamine induce heat shock protein HSP72 in injured neurons in posterior cingulate and retrosplenial cortex.

MK-801 and ketamine are noncompetitive N-methyl-D-aspartate (NMDA) receptor blockers that decrease brain injury in animal models of focal and global ischemia. Recent reports, however, suggested that MK-801 itself can damage neurons. Here we show that MK-801 (0.1 to 5.0 mg/kg) and ketamine (40 to 100 mg/kg) typically induce heat shock protein HSP72 mainly in layer 3 neurons of the posterior cingulate and retrosplenial cortex of the rat. These HSP72-immunoreactive neurons contain abnormal cytoplasmic vacuoles visualized by electron microscopy. The HSP72 immunoreactivity is maximal at 24 hours with 1.0-mg/kg doses of MK-801 and disappears by 2 weeks. Based on these data, we propose: (1) MK-801 and ketamine injure selected neurons, which express HSP72 in response to that injury. (2) Since HSP72 is induced for 1 to 2 weeks, the prolonged psychological side effects of MK-801, ketamine, phencyclidine, and related drugs could be related to this injury. (3) The neuroprotective effect of MK-801 is probably not related to HSP72 induction. (4) HSP72 immunocytochemistry is useful for studying nonlethal neuronal injury from a wide variety of brain insults.

Animals↗
PubMed1991

Chromosome 1 Charcot-Marie-Tooth disease (CMT1B) locus in the Fc gamma receptor gene region.

The Charcot-Marie-Tooth disease (hereditary motor and sensory neuropathy) loci have been reported to be on at least three chromosomes: 1 (CMT1B, HMSN1B), 17 (CMT1A), and X (CMTX). In this study multipoint linkage analysis of two Duffy-linked families given a combined LOD score of 8.65 to establish that the Duffy-linked CMT1B gene exists in the 18 centimorgan region between the antithrombin III gene and the Duffy/sodium-potassium ATPase loci. The simultaneous segregation of polymorphisms near the CMT1A locus on chromosome 17 excludes linkage to this chromosome region in both families. Polymorphic sites that flank the CMT1B gene have been subchromosomally localized to the proximal chromosome-1 long arm (1q21.2----1q25) by spot blot analysis of sorted chromosomes, polymorphic deletion analysis, in situ hybridization, and multipoint linkage analysis.

Antigens, Differentiation↗
PubMed1991

Immunohistochemical detection of DNA alkylation adducts in rat and hamster liver after treatment with dimethylnitrosamine.

Monoclonal and polyclonal antibodies specific for methylation adducts have been applied in an immunohistochemical study of DNA damage in rat and hamster liver following exposure to dimethylnitrosamine. The approach was validated, for frozen and paraffin-embedded sections, by comparison with biochemical data on adduct levels in whole tissues or specific cell populations in the same experimental systems. The potential application of this method to human exposure assessment is discussed.

Alkylation↗
PubMed1991

Environmental mutagens that induce the adaptive response to alkylating agents in Escherichia coli.

Many microorganisms exhibit an adaptive response to mutagenic alkylation damage. In Escherichia coli the response is regulated by the inducible Ada protein. A sensitive immunoassay employing two anti-Ada monoclonal antibodies has been developed here to monitor low levels of induction of the Ada protein. This protein was detected in non-induced E. coli which contained an average of two molecules of Ada per cell. The occurrence of the adaptive response in bacteria signals the existence of an ecological niche in which cells are exposed to direct-acting methylating compounds, but the structure and identity of these agents are unknown. Using the immunoassay to search for possible candidates, a number of methylating agents and precursors of such agents have been investigated. Carbamyl phosphate and methylamine yield N-methylurea, which reacts subsequently with nitrite to generate the strong inducer N-methyl-N-nitrosourea. The antibiotic streptozotocin also is a potent inducer of the adaptive response. Moreover, the abundant environmental mutagen methyl chloride acts as an inducer.

Adaptation, Physiological↗
PubMed1991

The influence of branched chain amino acids on colonic atrophy and anastomotic strength in the rat.

Conventional solutions of parenteral nutrients fail to reverse the colonic atrophy caused by starvation. This may be due to the absence from these solutions of the amino acid glutamine--a fuel for rapidly dividing cells such as colonocytes and fibroblasts. Although glutamine is unstable in solution, the infusion of branched chain amino acids (BCAA) increases the rate of synthesis and release of glutamine from skeletal muscle. We evaluated the hypothesis that the infusion of BCAA into undernourished rats would reduce the extent of mucosal atrophy and enhance the healing of anastomoses in the colon. Undernourished rats were randomized to receive 6 days of either a normal diet (Chow), conventional parenteral nutrition (CPN), or CPN supplemented with 1.8% BCAA (BCAA). The BCAA group had a higher plasma glutamine concentration than the Chow group (P less than 0.05). Compared with the CPN group, the BCAA group had the greater colonic mucosal weight (P less than 0.05) and colonic mucosal protein content (P less than 0.05), but there were no significant differences between groups in the bursting wall tension of the colon or the hydroxyproline content of the anastomoses. Although the infusion of BCAA has a beneficial effect on colonic atrophy, this did not result in the more secure healing of colonic anastomoses in this experimental model.

Amino Acids↗
PubMed1991

Efficacy of acemannan in treatment of canine and feline spontaneous neoplasms.

Forty-three dogs and cats with spontaneous tumors were treated with the immunostimulating polysaccharide acemannan by intraperitoneal and intralesional routes of administration. Tumors from 26 of these animals showed histopathological evidence of immunological attack as shown by marked necrosis or lymphocytic infiltration. Thirteen showed moderate to marked tumor necrosis or liquefaction. Twenty-one demonstrated lymphoid infiltration, and seven demonstrated encapsulation. Twelve animals showed obvious clinical improvement as assessed by tumor shrinkage, tumor necrosis, or prolonged survival; these included five of seven animals with fibrosarcomas. It is believed that acemannan exerts its antitumor activity through macrophage activation and the release of tumor necrosis factor, interleukin-1, and interferon.

Adjuvants, Immunologic↗
PubMed1991

Activity of O6-alkylguanine-DNA alkyl transferase in the liver, kidney and white blood cells of rats of different ages.

Age-related differences in the sensitivity of rats to alkylating carcinogens may be dependent on various factors, including the cellular levels of O6-alkylguanine-DNA alkyltransferase (AT). In the present study, the levels of AT were measured in protein extracts prepared from liver, kidney and peripheral white blood cells of male outbred rats aged 1, 4, 14, 22 and 36 months. The AT level (expressed as activity per milligram protein) in liver extracts was lower in rats aged 1, 4 or 36 months than in extracts prepared from rats aged 14 or 22 months. This observation of a variation in AT level with age is in agreement with our previous results. The AT levels in kidney and white blood cells did not differ significantly with age, and in all cases the AT levels were lower than those observed in the liver extracts, the kidney extracts having more AT activity than the white blood cell extracts. The total protein content of both liver and kidney tissues, calculated per gram of wet tissue, increased to a maximum at 14 months and subsequently declined, the total protein content being always higher in the liver than in the kidney. In contrast, the DNA content per gram of wet tissue was highest in young animals and subsequently declined to a minimum at 14 months. The implications of this inverse relationship to the levels of AT activity are discussed.

Age Factors↗
PubMed1991

Dental School of Copenhagen.

The Royal Dental College of Copenhagen, now a 101-year-old institution, has a yearly intake of around seventy students. The school is at the forefront of dental education in Europe with regard to facilities, research and curriculum development.

Denmark↗