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Biomedical subjects

M Roos

Publications and source records attributed to M Roos.

At least 73 records · Page 4Linked to original sources
PubMed1994

Electrical properties of mammalian lens epithelial gap junction channels.

PURPOSE: To establish an "electrical fingerprint" for the gap junction channels between mammalian lens epithelial cells. METHODS: The double whole cell patch clamp technique was applied to isolated cell pairs obtained from mouse lens epithelium and a continuous cell line of lens epithelial cells derived from the sheep lens (SLE 2.1). RESULTS: The junctional conductance in mouse lens epithelial cells and in cultured SLE 2.1 cells was found to be moderately voltage dependent. SLE 2.1 cells were analyzed in more detail. The voltage dependence could be described by a Boltzmann distribution with Vo = +/- 63.1 mV and Gmin = 0.34. In cell pairs that exhibited spontaneously low junctional conductance, single channel events could be distinguished. Single gap junction channel currents had a linear current-voltage relationship. A frequency histogram of single channel conductances from eight cell pairs had three major peaks of 35, 60 and 97 pS. CONCLUSION: The electrical properties of gap junction channels between mammalian lens epithelial cells were virtually identical to those previously reported for transfected cell lines expressing connexin43. The authors' physiological data are therefore in agreement with molecular studies that have identified connexin43 as the major connexin of lens epithelial cells.

Animals↗
PubMed1993

[Comparative use of MESAM IV and polysomnography in sleep-related respiratory disorders].

The high prevalence of sleep-related respiratory disturbances among the male population requires development of reliable outpatient measurement systems enabling the selection of patients to be admitted to the sleep laboratory. MESAM IV is such a system. It can record for up to 18 hours via four sensors a patient's snoring sounds, heart rate, oxygen saturation and posture. To test the reliability of the instrument we compared parallel night measurements by MESAM IV and polysomnography (PSG) via the respective Respiratory Disturbance Indices (RDI = number of apnoeas plus hypopnoeas per hour). The group of subjects studied numbered 68 patients of the sleep laboratory suspected of having sleep-related respiratory disturbances (age 18-78 years, average 50.8 yrs.; height 164-192 cm, av. 175.2 cm; weight 40-160 kg, av. 99.3 kg; body mass index 13.8-49.5, av. 32.3). Assessment of the MESAM measurements was effected on the one hand by means of a computer programme (version 1.2) that is part of the system, and on the other hand by 3 independent evaluators, two of whom were already experienced in MESAM evaluation. Each evaluator was unaware of all personal and clinical data of the patients and of the results obtained by the other evaluators. Visual assessment was performed according to fixed criteria with the inclusion of all four measurement signals of the system, whereas two mutually independent respiratory disturbance indices (RDI) were calculated by computer evaluation. The results of the various MESAM IV evaluations were compared with those of polysomnography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

[Sleep disorders and use of psychotropic drugs in 6-year-old children].

The purpose of this prospective survey, conducted over a two years period, was to study the use of psychoactive drugs among six year-old children in the Bas-Rhin administrative "département", of eastern France. The factors analysed were family environment, after-school time, the child's sleep, the locality where the child lived and the drugs used. The child was examined by school doctors, in the presence of the parents, at the compulsory consultation at the start of first-year infant school. The study was exhaustive. Of the 11,274 children examined, 12.1% used a psychoactive drug, although only 1% were considered by their parents to be suffering from insomnia. Of the children using drugs, 32% had used them for more than a year, 24% for more than two years and 11% for more than three years. Consumption was also shown to vary greatly between different localities; in some areas the proportion of children using drugs was more than 50%.

Child↗
PubMed1990

Risk factors for progression of human immunodeficiency virus (HIV) infection among seroconverted and seropositive homosexual men.

For identification of risk factors for progression of human immunodeficiency virus (HIV) infection, 746 homosexual men participating in a cohort study in Amsterdam, The Netherlands, were studied since October 1984. A total of 234 of these men were HIV antibody-positive at baseline, and 52 seroconverted during follow-up. These 286 individuals were categorized as high- and low-risk for progression to the acquired immunodeficiency syndrome (AIDS) on the basis of the presence or absence of HIV antigenemia, antibody to HIV core antigen, or a number of T helper lymphocytes less than 0.5 x 10(9)/liter during three or more subsequential blood samples. Ninety-six (41%) of the seropositives and 32 (62%) of those who seroconverted remained low-risk throughout the study period. Bivariate analyses revealed that educational level and a history of herpes zoster were associated with a low- and high-risk status, respectively. In multivariate analyses, a history of herpes zoster and a history of sexual intercourse with a person who had AIDS were associated with a more rapid disease progression. While herpes zoster is considered to be a marker of progressive immunodeficiency, a history of having sexual intercourse with a person who had AIDS points to the more virulent properties of HIV in these persons. Because both seropositives and seroconverters who had sexual intercourse with a person with AIDS had a more rapid disease progression, it seems plausible that being infected by a person with AIDS is a risk factor for a relative short incubation period.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Prepubescent hormonal control of the development of accessory olfactory bulbs in the male rat.

The effects of androgen treatment (TP) from postnatal day 20 (P20) onwards on the accessory olfactory bulbs' (AOB) development were studied in rats orchidectomized at birth (PO) or on P20. TP failed to restore impaired AOB development in the rats castrated at PO but completely restored AOB development in those castrated at P20. Androgen secretion during both the perinatal and prepubescent periods appeared to be critical for male AOB development.

Aging↗
PubMed1989

The primary structure of a feline class I gene: striking similarity to HLA-A.

The sequence of a feline class I pseudogene and its comparison with class I genes from other species is presented. The gene isolated is a pseudogene because of the presence of four stop codons and two frame shift mutations in the first- and second-domain encoding exons, as well as a mutation in a splice acceptor site in the third intron. By sequence comparison with the other class I sequences determined to date, the FLA pseudogene is most closely related to the HLA-A locus products (88% nucleotide identity.

Amino Acid Sequence↗
PubMed1989

Studies on sex dependency of B-cell susceptibility to streptozotocin in a rat model of type II diabetes mellitus.

Non-insulin-dependent (Type 2) diabetes in the rat can be induced by a neonatal injection of streptozotocin (STZ). At adult age male rats are more severely affected than female rats. Such difference could be due to a sex-related dissimilarity in susceptibility to STZ; this possibility was investigated in the present study. Incubation of isolated islets from male and female rats with STZ for 30 min, followed by tissue culture for 24 h, induced a dose-dependent decrease in insulin content that was similar in islets of both sexes. STZ in vivo, injected i.p on the second day of life, markedly enhanced blood glucose levels and reduced pancreatic insulin content when measured 2-12 days after the STZ injection. The parameters of B-cell damage did not differ, however, between male and female pups. Testosterone treatment, when started two days after the STZ injection, significantly accentuated hyperglycemia in both sexes during the second week of life. Body weight and pancreatic insulin content were not affected by the testosterone treatment. In conclusion, B-cell susceptibility to STZ in vitro or in vivo, during the neonatal period, is not influenced by gender. The hyperglycemic effect of testosterone indicates that the rise in androgens, starting with puberty, is at least partially responsible for a more severe diabetic state in male than in female rats at adult age.

Androgens↗
PubMed1989

Low AIDS attack rate among Dutch haemophiliacs compared to homosexual men: a correlate of HIV antigenaemia frequencies.

A cohort of 180 haemophiliacs followed between 1983 and 1986 and a cohort of 961 homosexual men followed between 1984 and 1986 were compared for the prevalence and incidence of HIV-1 antibody (HIV-1-Ab) seropositivity, the incidence of AIDS-related complex (ARC) and AIDS and the prevalence and incidence of serological and immunological markers for HIV-related disease progression. Among the haemophiliacs 23 (12.8%) patients were HIV-1-Ab seropositive at entry and 20 (12.7%) of the remaining 157 seroconverted for HIV-1-Ab during follow-up. Of the homosexual men 238 (24.8%) were HIV-1-Ab seropositive at entry and 68 (9.4%) of the 723 at entry seronegatives seroconverted during follow-up. Clinical follow-up of the HIV-1-Ab seropositive and seroconverted men was 59 months in the haemophiliac cohort and 60 months in the homosexual cohort. Among the HIV-1-Ab seropositive and seroconverted haemophiliacs and homosexual men the cumulative ARC/AIDS incidence was 2 and 18%, respectively. Occurrence of HIV-1-antigenaemia was more frequent among seropositive and seroconverted homosexual men (28%) than among haemophiliacs (7%) (p = 0.001). The groups did not differ significantly for the absence or loss of anti-HIV core antibodies or the occurrence of low CD4+ cell numbers. These data indicate a slower progression of HIV-related disease in seropositive haemophiliacs compared to seropositive homosexual men.

AIDS-Related Complex↗
PubMed1989

Effect on plaque growth and salivary micro-organisms of amine fluoride-stannous fluoride and chlorhexidine-containing mouthrinses.

Amine fluoride-stannous fluoride mouthrinse was tested in a double-blind cross-over clinical trial on 16 healthy subjects. Chlorhexidine mouthrinse prepared in the same colour and taste was used as the control. After a preparatory phase of 2 weeks, during which the subjects' plaque and gingival indices were reduced to zero by professional cleaning, 1-week test periods without mechanical cleaning were started in random order. The fluoride test solution did not prevent plaque accumulation and growth of salivary S. mutans and lactobacilli as did chlorhexidine. Furthermore, the plaque wet weight was statistically highly significantly greater during test periods of fluoride rinsing than during the chlorhexidine phase. The cleansing effect, as subjectively estimated by questionnaire, was in favour of chlorhexidine, but discolorations of teeth were assessed as significantly worse during chlorhexidine periods. Neither of the test solutions showed any effect on salivary flow rate, pH, buffering capacity, or lysosomal enzyme activity.

Adult↗
PubMed1989

[Borderline cases of sudden deafness and so-called vestibular dysfunction].

Forty-seven patients (31 male, 16 female) have been treated at the ENT University Clinic of Marburg during the last 13 years for sudden sensorineural hearing loss combined with disorders of equilibrium. The epidemiological data, history, audiological and electronystagmographic findings of those patients with cochleovestibular lesions are reported. The results of follow-up examination are compared with those of the patients who suffered from sudden deafness and vestibular neuronitis. In patients with combined lesions, special attention was paid to any correlation between the hearing loss and the dysequilibrium, on the one hand, and the restitution of both functions, on the other. We discuss how these patients with cochleovestibular lesions may be distinguished from those with Menière's disease.

Audiometry, Pure-Tone↗
PubMed1989

[The use of the residual range as the exclusive energy parameter in electron dosimetry].

A commonly used procedure to determine the absorbed dose to water in a high energy electron beam is based on the assumption that the response of an air-filled plane parallel chamber for this quantity is only a function of the difference between practical range and measuring depth (the residual range). This procedure is said to be applicable to almost all electron energies and spectra in practical use. The response of a plane parallel chamber in a water phantom was determined by means of ferrous sulphate dosimeters in radiation fields of a linear accelerator. The results show that the residual range is insufficient as the only energy parameter.

Electrons↗