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At least 613 records · Page 34Linked to original sources
PubMed1998

A fast-freezing device with a retractable environmental chamber, suitable for kinetic cryo-electron microscopy studies.

The design and construction of a fast-freezing device are described. A polycarbonate chamber, in which the humidity and temperature are controlled by microprocessors, slides on a robust chassis guided by ball or Teflon bushings. In its freezing position, the chamber rests on top of the cryogen vessel. The specimen is therefore frozen directly from the experimental conditions within the chamber without exposure to the external environment. After freezing, the chamber, but not the specimen, rises automatically, vacating space for handling the specimen. The chamber, the shutter, and the specimen are all driven pneumatically at an adjustable speed of up to approximately 10 m s-1 and coordinated by either pneumatic or electronic logical gates. Provisions are made for automatic blotting, spraying, and flashing. The chamber is compatible with a liquid nitrogen-cooled copper block assembly for impact (slam) freezing for freeze-substitution and freeze-fracture.

Cryopreservation↗
PubMed1998

Human hemoglobin adducts following exposure to hexahydrophthalic anhydride and methylhexahydrophthalic anhydride.

Hexahydrophthalic anhydride (HHPA) and methylhexahydrophthalic anhydride (MHHPA) are highly allergenic compounds used in the chemical industry. The aim of this study was to characterize the protein adducts in erythrocytes following exposure to HHPA and MHHPA. Blood and urine samples were obtained from 51 HHPA- and MHHPA-exposed workers. Erythrocytic proteins from HHPA- and MHHPA-exposed workers were fractionated by gel filtration and ion exchange chromatography. In vitro synthesized conjugates between tritium-labeled and unlabeled HHPA and hemoglobin (Hb) were hydrolyzed by acid or digested by Pronase E. Levels of in vivo formed anhydride-Hb adducts and urinary/plasma levels of the corresponding acids were analyzed by gas chromatography-mass spectrometry (GC-MS) and correlated. The decay of adducts was studied in workers leaving employment or during vacation. More than 85% of the adduct forming protein in vivo coeluted with Hb in gel filtration and ion exchange chromatography. At least 70% of the HHPA in the in vitro formed adducts was found on lysine by GC-MS. Similar findings were obtained using Pronase E-digested tritium-labeled Hb-HHPA. The adduct levels in workers ranged 0-26 pmol/g Hb (mean 2. 7 pmol/g Hb) for HHPA, and the range for MHHPA was 0-55 pmol/g Hb (mean 4.1 pmol/g Hb). The Spearman's rank correlation coefficient between urine data and adducts was for HHPA rs = 0.80 and for MHHPA, rs = 0.78. For the plasma, the correlation using HHPA data was rs = 0.80 and for MHHPA, rs = 0.69. The adducts seemed to be stable in vivo. The adduct levels may be used as biomarkers of exposure to HHPA and MHHPA.

Allergens↗
PubMed1992

A mechanism of passive immunization with monoclonal antibodies to a 185,000 M(r) streptococcal antigen.

The cell surface streptococcal antigen (SA) I/II of 185,000 M(r) is an immunodominant molecule that expresses one or more adhesion determinants. A series of 14 monoclonal antibodies (MAb) to defined parts of SA I/II were generated and some of these were used in passive immunization of macaques. Topical administration of selected MAb to the teeth of macaques prevented colonization of endogenous or implanted exogenous Streptococcus mutans for a period of 1 year. Significant reduction of both smooth surface and fissure caries was found in macaques who had MAb (Guy's 1) applied to their teeth, as compared with saline-treated animals. A series of in vivo passive immunization experiments was then carried out in 57 human subjects. Topical application of MAb to SA I/II prevented colonization of both artificially implanted exogenous strains of S. mutans, as well as natural recolonization by indigenous S. mutans. The properties of the protective MAb were then investigated and the epitope specificity within the SA I/II molecule was found to be essential but not the isotype specificity of the immunoglobulin (Ig). The requirement for complement activating and the phagocyte binding sites of the Fc fragment of MAb was not essential, as the F(ab')2 fragment of the MAb was as protective as the intact IgG, but the Fab fragment failed to prevent recolonization of S. mutans. Prevention of recolonization was specifically restricted to S. mutans, as the proportion of other organisms, such as S. sanguis, failed to show a significant change. The surprising feature of these experiments was that protection of re-colonization of S. mutans lasted up to 2 years, although MAb was applied for only 3 weeks and functional MAb was detected on the teeth only 3 days following application of the MAb. The long-term protection could therefore not be accounted for by a persistence of MAb on the teeth, but may be due to a shift in the microbial balance in which other bacteria occupy the ecological niche vacated by S. mutans, resulting in colonization resistance to S. mutans. Gene cloning and sequencing the SA from S. mutans, S. sobrinus and S. sanguis identified a conserved region (residues 955-1213) which on Southern hybridization and partial DNA sequence analysis was also found in 19 alpha-haemolytic oral streptococci. The results suggest that the SA molecule may constitute a family of adhesins in oral alpha haemolytic streptococci.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Internal regulations and general guidelines of a neurosurgical department and training programme.

It is strongly recommended that general guidelines and internal regulations be laid down in written form by the department. The guidelines regulate the general workflow and related trainee duties and responsibilities, education and research, special procedures for particular diseases and conditions (standards of care). Regarding general workflow of the department, the following items should be laid down once in written form: time table of department, working hours, admission procedures, medical records directives, responsibilities on wards and in the emergency unit, patient information, discharge procedures, outpatient consultations, call schedule and on-call duty plan, as well as week-end and holiday regulations for rounds on wards and ICU. Regarding education and research, the following items should be written down: conferences and teaching rounds, policies on presentations and publications, policies regarding meetings and courses, research leave and vacation plan. The written definition of standards of care is still considered optional in neurosurgery at the present time.

Certification↗
PubMed1992

Seasonal variation in gonorrhoea.

Seasonal variations in the incidence of gonorrhoea were observed in the 1970's with a peak in the third quarter of the year and a trough in the first and fourth quarters. The aim of this study was to determine what, if any, seasonal trends were present in Scotland and Lothian between 1984 and 1989 and postulate mechanisms to explain our observations. We observed a change in the previously reported pattern with regular peaks of infection in the first and third quarters of the year for Scotland but no regular trend in the Lothian region. The most likely explanation for the observed trends are changes in sexual behaviour related to summer vacations and seasonal work patterns but other unidentified factors probably also contribute.

Female↗
PubMed1980

Alterations in axons and synapses of olfactory cortex following olfactory bulb lesions in newborn rats.

The olfactory cortex of rats is being studied at various survival times following deafferentating olfactory bulb ablation on the day of birth. The neonatal axons and synaptic terminals undergo rapid, flocculent degeneration and fragmentation. Most are not electron-dense and therefore probably not argyrophilic at this particular age of the lesion. The degeneration and removal of debris is far more rapid than in adults, yielding a markedly enlarged extracellular space with a relative absence of glia at the vacated postsynaptic "thickenings". Denervated postsynaptic "thickenings" become occupied by neuronal and nonneuronal profiles and profiles of uncertain origin, singly or in various combinations, or the sites may remain partially vacant. One or more axons with synaptic vesicles often aggregated at the site are commonly involved. Certain terminals form contacts on progressively greater lengths of the "thickening" until typical synaptic contacts predominate by 14 days survival. The results suggest a competitive reinnervation process and provide a fine structural explanation for the events leading to alterations in this pathway following neonatal deafferentation.

Age Factors↗
PubMed1984

Urinary excretion of chromium as an indicator of exposure to trivalent chromium sulphate in leather tanning.

Two workers exposed to trivalent chromium sulphate in a leather tannery had high concentrations of chromium in the urine. The concentration of chromium showed a workshift-related diurnal fluctuation, but it was remarkably high even after a vacation, indicating accumulation of chromium in the body. The concentrations of chromium in the workplace air, as collected on filters using standard techniques, were below 30 micrograms/m3. The chromium in the air was present in the form of large droplets not collected by the standard techniques. In the blood stream, chromium was transported exclusively in the plasma. No absorption of chromium through the skin could be detected. Absorption from the gastrointestinal tract was calculated to explain the findings.

Adult↗
PubMed1985

Exposure in welding of high nickel alloy.

Nickel (Ni) levels in air during welding of high-Ni alloy (75% Ni) were very high (mean 0.44 mg/m3, range 0.07-1.1 mg/m3; 20 person-days of measurements). In six welders the Ni level in urine after four weeks of vacation was slightly but statistically significantly enhanced as compared to ten unexposed controls (means 8.7 vs 5.1 micrograms/l; P less than 0.005). The level on Monday mornings increased somewhat during a period of six weeks of high-Ni alloy welding (mean 13 micrograms/l; P less than 0.05). The level was slightly higher Thursday afternoon (mean 18 micrograms/l; P less than 0.0001). The data indicate the existence of a very slow pool of Ni in the body in addition to a faster one. There was no correlation between Ni levels in air and urine. Thus, in spite of the very high Ni levels in air, urinary Ni levels were thus of little use for biological monitoring of exposure and risk during high-Ni alloy welding. All eleven welders studied reported one or more symptoms (irritation of upper airways, headache, tiredness) as occurring more often (P less than 0.006) during high-Ni welding than when welding ordinary stainless steel. Lung-functions studies were normal.

Adult↗
PubMed1988

Antipyrine and metronidazole metabolism during occupational exposure to gasoline.

Antipyrine and metronidazole clearance was measured in 18 fuel-filling attendants by the single-sample method while the attendants were being exposed occupationally to gasoline; the measurements were repeated after 2-4 weeks with no exposure. Eighteen office workers were investigated simultaneously. The median concentration of gasoline in the breathing zone of the fuel-filling attendants during filling and cleaning operations was 270 mgm-3 (range 18-1758 mgm-3). Antipyrine clearance was 18% higher during exposure to gasoline than after 2-4 weeks of vacation (P less than 0.01), while antipyrine clearance was unchanged in the office workers. No change was found in metronidazole clearance in either group. Antipyrine clearance was on average 26% higher in the smokers than in the nonsmokers (P less than 0.05), while metronidazole clearance was similar in smokers and nonsmokers. We conclude that gasoline is an inducer of antipyrine elimination, with no impact on metronidazole elimination. This indicates that gasoline has a differential inducing effect on the hepatic drug metabolizing enzymes of man.

Adult↗
PubMed1988

Enzymuria in workers exposed to inorganic mercury.

Urinary excretion of beta-hexosaminidase (NAG = N-acetyl-beta-glucosaminidase) and albumin was examined in 41 chlor-alkali workers exposed to inorganic mercury and 41 age-matched controls. Either U-HG or B-Hg levels for these workers were available dating from the 1960s to the present. Increased U-NAG was seen in workers with a U-Hg today of more than 4 micrograms/mmol creat (about 50 micrograms/l: 35 ug/g creat). Multiple linear regression analysis showed that U-NAG was correlated to U-Hg and integrated dose but not to the present B-Hg level. No albuminuria (detection limit 12.5 mg/l) was found in any of the subjects. In a longitudinal study, no decrease in U-NAG levels was seen in 15 chlor-alkali workers after their vacation (means = 20d). In five workers followed for ten months after a short exposure period, no definite time trend could be seen. The results show that there is a slight effect on renal tubules even at rather low levels of exposure to mercury vapour. The clinical significance of the enzymuria levels found here is, however, debatable.

Acetylglucosaminidase↗
PubMed1978

The microvibrations of the body, an index for examination stress.

Changes of whole-body microvibrations (MV) were quantitatively analyzed in 123 voluntary subjects during two examination situations and compared with the results obtained during the ensuing vacation. The force oscillations in the three space directions were measured during quiet bipedal standing and simultaneously recorded as a time function with the rectified and integrated force-time function (= rectified impulse). The rectified impulses related to body weight were used as a measure for the MV. Immediately before the examinations, all the subjects showed high values. These decreased significantly in the control measurement if the subjects passed the exams, but remained relatively high in the subjects who failed. In all three measurements, smokers and candidates who took tranquilizers before the exams show higher MV values than do the other subjects. Females are less tense than males, a difference particularly significant in the vertical (z) direction. The rectified impulse in this direction correlates positively with the estimated cardiac output. Body weight and body length show a positive correlation with the MV values in the horizontal forward-backward (x) and vertical (z) direction. The measurement of the whole-body MV enables quantitative evaluation of the complex load due to an examination situation. The hypothesis that different types of stress or personality affect given directions in space requires further investigation.

Adult↗
PubMed1986

Lung function and rhizopus antibodies in wood trimmers. A cross-sectional and longitudinal study.

Pulmonary function was studied in 66 wood trimmers exposed to organic dust (moulds) after a month of no exposure (summer vacation) and then three and 27 months later, and also during a working week. The results of forced expirometry and single breath nitrogen washout were compared with those obtained in local controls and in larger reference materials. The forced vital capacity (FVC) and forced expired volume in one second (FEV1) were reduced by an average of 0.4 and 0.31, respectively, after one month of no exposure, however, the nitrogen washout variables showed no clear changes. Repeated measurements three months later on a Monday morning after two days of no exposure showed a further reduction in FVC and FEV1 by an average of 0.21 in a sawmill with high exposure to moulds (10 colony-forming units/m3), but not in another sawmill with ten times lower exposure. Further recordings 27 months later (Monday morning before work) displayed no further worsening in any spirometric variable. No change in lung function was noted after one day of work (Monday morning to Monday evening), but a further reduction in FVC of an average of 0.31 was seen in non-smokers at the end of the week, with apparent resolution over the weekend. The impairment was more obvious at the sawmill with higher air concentrations of organic dust than at the other sawmill. It is concluded that wood trimmers may develop restrictive pulmonary dysfunction, which might be explained by an immunopathological reaction to heavy mould exposure.

Adult↗
PubMed1982

Uncommon extensive juxtacortical necrosis of the brain.

A previously healthy woman in middle age, vacationing in Spain, is treated with a massive dose of insulin for minimal hyperglycemia following an apparent gastrointestinal disease. This results in rapid coma and, 20 days later, in death. At autopsy, the main finding consists in a remarkable and uncommon ribbon-like juxtacortical necrosis of the white matter in both hemispheres of the telencephalon. There is also a microscopic focal necrosis in the pons cerebri. The grey matter of cortex and basal nuclei, and the subcortical arcuate fibers are spared. The detailed autopsy fails to reveal other essential changes. We have not been able to find reports on an identical case. Hypoglycemic coma usually causes cerebral lesions different from those seen in the present case. A brief analysis of the differential diagnosis is made. In the absence of unequivocal signs of infection, vascular disease or degenerative marks, the findings are tentatively related to complex interactions between fluid loss, hypoglycemic coma, hypoxia and other metabolic disturbances.

Brain↗
PubMed1984

Stress and the transformation of lymphocytes by Epstein-Barr virus.

Although various stressors appear to influence herpesvirus infections, the underlying mechanisms have not been studied. A prospective design was used to examine the effects of examination stress and loneliness on the transformation of B lymphocytes in mixed cultures of T and B lymphocytes by Epstein-Barr virus (EBV). Three blood samples were drawn from 42 EBV-seropositive medical students, with the baseline sample taken 1 month before their final examinations, the stress sample drawn on the first day of final examinations, and the third sample taken the first week after their return from summer vacation. A median split on the UCLA Loneliness Scale divided the subjects into high- and low-scoring loneliness groups. There were significant effects for change over trials, with the lowest transformation levels (i.e., more virus required to transform cells) found in the stress sample. There was also a significant main effect for loneliness, in which high loneliness was associated with lower transformation levels. Possible immunological pathways for the observed changes are discussed.

Antibody Formation↗
PubMed1988

A family outbreak of hemolytic-uremic syndrome associated with verotoxin-producing Escherichia coli serotype O157:H7.

All five siblings (three boys and two girls, aged 1.5-9 years) in a family developed hemolytic-uremic syndrome associated with verotoxin-producing Escherichia coli O157:H7 at a lakeside vacation cottage during the fall of 1985. All five were hospitalized and made a full recovery. Both parents remained asymptomatic, and neither had evidence of this infection. In four children who were investigated prospectively, free verotoxin was still detectable in the stools for between 3 and 7 weeks. The prodromal diarrheal illness in the children occurred over a 10-day period. The epidemic curve was consistent with a point-source outbreak, but continuous exposure or person-to-person transmission could not be ruled out. The source of the infection was not identified.

Bacterial Toxins↗
PubMed1985

Stress, loneliness, and changes in herpesvirus latency.

This study used a prospective design to examine the influence of examination stress and loneliness on herpesvirus latency as measured by changes in antibody levels to three herpesviruses, Epstein-Barr virus (EBV), Herpes simplex type I (HSV-1), and cytomegalovirus (CMV). Three blood samples were obtained from 49 first-year medical students, with the first sample drawn 1 month before final examinations, the second on the first day of final examinations, and the third during the first week after their return from summer vacation. A median split on the UCLA Loneliness Scale divided subjects into high- and low-scoring loneliness groups. There were significant changes in the antibody titers to all three herpesviruses across the sample points, with the lowest levels found in the third (low stress) sample. High-loneliness subjects had significantly higher EBV antibody titers than low-loneliness subjects. These data suggest that stress-related immunosuppression can significantly modulate herpesvirus latency.

Adult↗
PubMed1993

Ultrastructural observations of host-cell invasion by sporozoites of Eimeria papillata in vivo.

Scanning and transmission electron microscopy were used to study the invasion of mouse small-intestinal epithelium by sporozoites of Eimeria papillata. Some mice received oocysts by gavage and others received either sporocysts or sporozoites by direct injection into the small intestine. The highest concentration of invaded cells were found in ligated intestinal tissues studied at 5-45 min after the inoculation of sporozoites. Sporozoites actively invaded anterior end first, which resulted in extensive damage to the host cell. Such cells showed disrupted microvilli; protuberances of cytoplasm into the lumen, apparently the result of a disrupted plasma membrane; vacuolization of the cytoplasm; and damage to the mitochondria. These damaged cells were rapidly vacated as the sporozoite moved laterally into one or more adjacent intact host cells without entering the lumen. It is suggested that the host cell initially entered from the lumen becomes so severely traumatized that the parasite of necessity enters an adjacent cell as a prelude to further development. Various aspects of host-cell invasion by coccidia and malarial parasites are reviewed.

Animals↗
PubMed1984

Age-related fine structural changes in axons and synapses during deafferentation of the rat pyriform cortex: a possible basis for plasticity.

The purpose of this study was to compare the sequence of axonal and synaptic alterations following deafferentating lesions at selected postnatal ages and relate these changes to synaptic organization in the olfactory cortex. Rats received unilateral olfactory bulb ablation at 2 1/2, 6, 9 and 13 days of age and were studied at survivals of 12 h to 30 days. At least three clearly different forms of acute degeneration were seen; flocculent, granular and dense with the granular form an intermediate form. The proportion of granular and especially dense degeneration increases after six days of age as does the presence of glia. The denser the type of degeneration, the greater the retention of remnants of this form of synaptic degeneration at deafferented postsynaptic sites. This as well as the increased presence of glia after six days may be important factors in the limitation of plastic reorganization or reinnervation in more mature individuals. The youngest operated animals show rapid vacating of the receptor site, relative absence of glia and striking evidence of competitive reoccupation of deafferented sites.

Age Factors↗