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Biomedical subjects

T Albrecht

Publications and source records attributed to T Albrecht.

At least 127 records · Page 7Linked to original sources
PubMed1985

[The effect of various ventilation conditions on evoked potentials of the visual cortex of the cat in distention of the stomach].

In 10 cats anaesthetized using chloralose and with muscular relaxation by gallamine and continuous artificial ventilation in acute experiments photically evoked potentials (PEP) were recorded from the visual area of the cortex under different intragastric pressures and varying tidal volumes. It was the aim of this study to examine whether an exteroceptive stimulus (light flash) in the visual analyzer, which is influenced by an interoceptive stimulation (gastric pressure), may also be modified by different tidal volumes. Times, amplitudes and slope parameters, blood pressure and heart rate of the animals were studied. The PEP of the visual cortex was modified under the influence of the interoceptive stimuli. It could, however, be shown that already hypo- and hyperventilation alone may cause alterations in the latency period of the PEP. They arise in a different manner in individual parts of the measured parameters of the PEP and do not change these values in a typical manner. Additional dilatation of the stomach may suppress the phenomena caused by alterations in the tidal volume. Thus, attention should be paid to both blood gases and acid base balance in animals in studies on viscero-cerebral interrelationships as well as to interactions between different analyses using the method of evoked potentials.

Animals↗
PubMed1983

Similarities between cytomegalovirus-induced cell rounding and contraction of smooth muscle cells.

Cytomegalovirus infection of human fibroblastic cell cultures resulted in rounding of the cells and a subsequent decrease in their size. Smooth muscle relaxing agents such as papaverine, hydralazine, diazoxide, nitroprusside and verapamil blocked these early cytopathogenic effects suggesting that cell rounding results from a contractile-like response involving an influx of calcium ions.

Cytomegalovirus↗
PubMed1983

Reduction of 4-nitroquinoline 1-oxide to 4-hydroxyaminoquinoline 1-oxide in lysates of cytomegalovirus-infected cells.

The rates of virus inactivation by 4-nitroquinoline 1-oxide (NQO) and 4-hydroxyaminoquinoline 1-oxide (HAQO) were compared and samples of cytomegalovirus (CMV)-infected cell lysates to which NQO had been added were examined for the presence of HAQO. These experiments demonstrated that (i) CMV inactivation by HAQO was more rapid than with NQO, (ii) virus inactivation by either NQO or HAQO failed to demonstrate a photodynamic component, and (iii) NQO-treated stocks contained HAQO, indicating reduction of NQO to HAQO. The results support the concept that metabolism of NQO to HAQO enhances the genotoxic effect of NQO.

4-Hydroxyaminoquinoline-1-oxide↗
PubMed1982

Characterization of human cells persistently infected with cytomegalovirus and exposed to a chemical carcinogen.

A non-productive, persistent human cytomegalovirus (CMV) infection was developed in human embryo lung (LU) cells by initially using supraoptimal temperatures to restrict the replication of a recent CMB isolate (76-24). Although CMV replication was observed in some cells within a few weeks of shifting the cultures to 37 degrees C and subculturing, CMV cytopathic effects and infectious CMV were not detected with further subculturing during the next 5 weeks. CMV-specific nuclear antigens were, however, observed in most cells (designated LU-76-24) for 38 additional culture passages made during the following 12 months. Although the LU-76-24 cells were morphologically distinct from LU cell cultures carried in parallel as controls, the LU-76-24 were contact-inhibited in spite of a somewhat disoriented growth pattern. Treatment of LU-76-24 cells with 0.05 microgram/ml of the chemical carcinogen 4-nitroquinoline 1 oxide (NQO) induced a lytic CMV infection from which a clone of cells (designated LUC-NQO) was isolated. No effect was seen when LU cells were treated with the same dose of NQO. LUC-NQO cells were morphologically altered from LU-76-24 cells and had lost contact inhibition. Even though CMV-specific nuclear antigens were observed in LUC-NQO cells, infectious CMV was not detected in lysates of these cells, nor was CMV rescued by co-cultivation of these cells with susceptible cells or by induction with 5-iodo-2'-deoxyuridine. LUC-NQO, but not LU or LU-76-24 cells, plated with good efficiency in semi-solid medium. The results indicate that long-term, non-productive, persistent CMV infections can be established in vitro and suggest that such cells may be more susceptible than non-infected cells to the action of chemical carcinogens.

4-Nitroquinoline-1-oxide↗
PubMed1982

[Effect of interoceptive stimulation of the stomach on photically evoked potentials of the visual cortex with reference to blood pressure and heart rate in the cat].

In ten chloralose narcotized, relaxed and constantly oxygenated cats the stomachs were dilated with two different pressures in acute experiments. Photically evoked potentials (PEP) were derived from the visual cortex of the animals. The aim of the work was to find out in which respect the processing of an exteroreceptive stimulus (light stimulus of only 200 ms) in the visual analyzer can be influenced by an interoceptive stimulation. Besides, it had to be established to which extent the visceral stimulation leads to a change of other vegetative parameters. Qualitative alterations of different PEP-parameters, blood pressure and heart rate of the experimental animals were examined at different stomach pressures. Changes of the positive and negative amplitudes and the time of the negative component of the primary complex of the evoked potential have been observed. Moreover, there could be registered an increase in blood pressure depending on the height of stomach pressure. The heart rate was not influenced. Further studies will have to clarify whether the changes of the PEP are produced by the interoreceptive stimulus or by the changes of blood pressure or respiration.

Animals↗
PubMed1981

Herpes virus inactivation by chemical carcinogens: differential inactivation of herpes simplex viruses by 4-nitroquinoline 1-oxide and related compounds.

Treatment of stocks of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) with the chemical carcinogen 4-nitroquinoline 1-oxide (NQO) resulted in inactivation of virus infectivity at rates which were directly dependent on the concentration of NQO and interval of exposure to NQO. HSV-1 strains were more sensitive than HSV-2 strains to inactivation by NQO, although survival curves of both HSV types were multicomponent. Exposure of HSV-2 to a related group of chemicals suggested that the structural specificity required for inactivation of this virus was similar to that established by previous in vivo carcinogenicity tests.

4-Nitroquinoline-1-oxide↗
PubMed1981

Cytomegalovirus: an ultrastructural study of the morphogenesis of nuclear inclusions in human cell culture.

We investigated the ultrastructural development and maturation of cytomegalovirus (CMV) nuclear inclusions (NIs) in human embryo thyroid cells at 1 to 144 h post-infection. At 5 h, most cells had rounded from an initial fibroblastic appearance and contained early NIs. At 24 h, early NIs were larger and better defined. At 48 h, although early NIs were still present, most cells had larger and presumably more mature NIs. These latter NIs consisted of several subunits, each made up of a fibrillar network enclosing an electron-lucent area which contained coarse and delicate granules. Also, at 48 h, virus particles were first seen in the nucleoplasm. At 72 h, in cells with more developed NIs, virus particles were closely associated with the fibrillar network. Between 96 and 144 h, the NIs reached maximum size and were made up of numerous subunits. The results indicate that two types of NIs coexist during CMV infection. The appearance of the early the late NIs coincides with the reported peaks of CMV DNA synthesis and thus may explain the biphasic pattern of DNA synthesis in CMV infection. Morphogenetic features of the NIs conform with the hypothesis that synthesis of CMV DNA may occur in the centre in each NI subunit and that the fibrillar network represents condensing capsid proteins.

Cells, Cultured↗
PubMed1980

Correlation of the chemical structure of 4-nitroquinolines inactivating human cytomegalovirus and established in vivo carcinogenicity tests.

Inactivation of the infectivity of human cytomegalovirus (CMV) and herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) has been observed following exposure to 4-nitroquinoline 1-oxide (NQO) or its metabolite, 4-hydroxyaminoquinoline 1-oxide (HAQO). The present study of the specificity of the chemical structure of 4-nitroquinolines demonstrated that both the 4-nitro and 1-oxide groups were required for inactivation of virus infectivity. Reduction of the 4-nitro group to a 4-hydroxyamino group enhanced activity, while further reduction to an amino group resulted in loss of activity against virus infectivity. The capacity to inactivate virus was also lost by substitution of the pyridine ring for the quinoline nucleus of NQO. The relationship between the chemical structure and the ability to inactivate viruses studied here correlates well with earlier in vivo carcinogenicity studies of the same group of chemicals.

4-Nitroquinoline-1-oxide↗
PubMed1980

Heterogeneous morphologic features of plaques induced by five strains of human cytomegalovirus.

Five strains of human cytomegalovirus (CMV) were examined in three human fibroblastic cultural systems with respect to plaque size and morphologic features. Plaques produced in cultures of fibroblastic cells from thyroid, and to a lesser extent in those from human embryonic skin-muscle tissue, had strain-associated morphologic differences that were stable on repetitive examination. The variations in morphologic characteristics of plaques appeared to reflect cytopathic changes, and the five strains could be separated on the basis of morphologic characteristics into two polar groups. Comparison of the sensitivities of three human fibroblastic cell lines for the detection of CMV revealed that one line was consistently inferior.

Antigens, Viral↗
PubMed1980

Replication of human cytomegalovirus at supra-optimal temperatures is dependent on the virus strain, multiplicity of infection and phase of virus replication.

The kinetics of replication of five strains of human cytomegalovirus (CMV) were studied to determine the influence of (i) temperature, (ii) virus strain, (iii) m.o.i. and (iv) cell type. Relative to growth at 37 degrees C (m.o.i. = 3 to 9) eclipse periods were extended from 24 to 48 h at 33 degrees C and to 72 h at 40.5 degrees C. Yields were reduced at 33 degrees C and almost eliminated at 40.5 degrees C. No replication occurred in most instances at 40.5 degrees C and with 0.05 p.f.u./cell. Temperature shift studies (40.5 to 37 degrees C) indicated that the block to replication at 40.5 degrees occurred about 12 to 16 h p.i. resulting in little synthesis of CMV DNA or late antigens. The degree of inhibition of late functions at 40.5 degrees C is virus strain and m.o.i. dependent, but is not dependent on the type of fibroblastic cell used. These data suggest that persistent CMV infections are favoured at 40.5 degrees C.

Antigens, Viral↗
PubMed1980

Cytomegalovirus: development and progression of cytopathic effects in human cell culture.

Cytopathic effects of cytomegalovirus infection were studied in human cell cultures at various time intervals. Cells derived from human embryonic thyroid, skin-muscle, and lung were infected with five different strains of cytomegalovirus at multiplicities of infection of approximately 5 plaque forming units per cell. Under these conditions, cell rounding and early cytoplasmic inclusions were first apparent at 5 hours postinfection, whereas nuclear inclusions were first observed as a homogenous eosinophilic bead at 24 hours postinfection. Cytoplasmic and nuclear inclusions underwent extensive morphogenesis through 96 to 120 hours postinfection. Development of nuclear inclusions included the formation of distinctive beadlike subunits, which increased in size from their first appearance at 48 to 72 hours postinfection and underwent apparent contraction and breakup after 96 hours postinfection. While the cytopathology induced by various cytomegalovirus strains studied was generally similar, the kinetics of their development was different and independent of both the multiplicities of infection and the source of the fibroblastic cells. Such cytomegalovirus strain-associated differences in cytopathology could result from variances in biologic characteristics of the strains studied.

Cell Nucleus↗
PubMed1979

Inactivation of human cytomegalovirus by the chemical carcinogen 4-nitroquinoline 1-oxide.

The infectivity of cytomegalovirus (CMV), strain Davis, was inactivated by 4-nitroquinoline 1-oxide (NQO). A series of survival curves indicates that the rate of inactivation was directly dependent on the concentration of NQO over a range of 5 to 200 microgram/ml. At concentrations of I microgram/ml or less, inactivation of virus stock was not observed and at concentrations in excess of 200 microgram/ml, the cellular toxicity of residual NQO prevented quantification of the relatively low surviving infectivity. At a concentration of 200 microgram/ml NQO or less, the loss of virus infectivity could be clearly shown to result from the interaction of NQO with virus and not with cells, since the addition of similar doses of NQO to assay cells simultaneously with virus did not adversely affect the sensitivity of the assay cells to measure virus infectivity. Similarly, the dimethylsulphoxide carrier at concentrations of 5% or less was shown to have a negligible effect on both virus infectivity and on the sensitivity of human skin muscle cells to assay virus infectivity. NQO inactivation of virus infectivity appeared to depend very little on white light, since the kinetics of inactivation in the presence and in the absence of white light were similar.

4-Nitroquinoline-1-oxide↗
PubMed1976

Induction of cellular DNA synthesis and increased mitotic activity in syrian hamster embryo cells abortively infected with human cytomegalovirus.

The effect of human cytomegalovirus (CMV) on cell DNA synthesis and mitotic activity in hamster embryo fibroblasts was examined. The results indicated that CMV infected cells had increased rates of cell DNA replication and mitotic activity. Detection of the effect of CMV on these two parameters necessitated arrest of cells prior to infection with low serum concentrations. This lowered the background levels of DNA synthesis and cell division so that the effect of virus infection could be detected. The data indicate that cells arrested prior to infection demonstrate increased susceptibility to virus infection. It was also observed that the effect of CMV on both DNA replication and mitotic activity could be enhanced by irradiation with ultraviolet light of the virus prior to infection.

Animals↗