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Biomedical subjects

J Althoff

Publications and source records attributed to J Althoff.

At least 55 records · Page 3Linked to original sources
PubMed1981

Electron-microscopic microprobe analysis on the initial stages of mineral formation in the epiphyseal growth plate.

Dry thin sections (300-500 nm thick) of shock-frozen, freeze-dried and embedded epiphyseal growth plates from the proximal tibia of guinea pigs were cut longitudinally from the plate. Dark round bodies (phi less than 0.5 micron) were observed using the scanning transmission mode of the electron microscope initially directly in the vicinity of the chondrocytes. They gradually spread out in the direction of the metaphysis to the center of the longitudinal septum and represent most probably the matrix vesicles. By use of a microscan of 0.25 X 0.25 micron the element-concentrations of these bodies were measured. The measurements started on those bodies that could be clearly recognized and were extended to a length of 30-40 micron in the metaphyseal direction. To obtain approximate quantitative results the registered CaK alpha and PK alpha x-ray counts were directly compared with counts of fully mineralized regions, the Ca and P contents of which are known. Ca as well as p could be detected in the first visible vesicle-like structures (Ca approximately 0.2%, P approximately 0.4%) and increased steeply in the metaphyseal direction, amounting to approximately 6% Ca and 3% P. These results may lead to the conclusion that Pi becomes split from phosphate esters and transformed into the matrix vesicles already in a very early stage of enrichment. Incorporation of Ca may be coupled with this process.

Animals↗
PubMed1981

The carcinogenic effect of nitrosomethyldodecylamine in European hamsters.

Laboratory-bred European hamsters received nitrosomethyldodecylamine (NMDA) subcutaneously in olive oil once weekly for life. The animals showed mainly mucoepidermoid carcinomas of the lung, carcinomas of the urinary bladder and squamous cell carcinomas and sarcomas at the injection site. The tumour incidence was 90% in males and 70% in females, while the average tumour latency was 32 +/- 6 weeks for both sexes. Males had an average survival time of 29 +/- 17 weeks and females 24 +/- 19 weeks.

Animals↗
PubMed1981

The carcinogenic effect of 1,1-diethyl-3-methyl-3-nitrosourea in European hamsters.

Laboratory-bred European hamsters received subcutaneous injections of 1,1-diethyl-3-methyl-3-nitrosourea once weekly for life. The animals developed mainly squamous cell carcinomas of the nasal and oral cavities and malignant sarcomas (schwannomas) of the glandular stomach. The average tumour latency was shorter in females (24 weeks) than in males (28 weeks), while tumour incidence was 80% for both sexes.

Animals↗
PubMed1981

Biological and chemical studies involving methyl-t-butylnitrosamine, a non-carcinogenic nitrosamine.

Methyl-t-butylnitrosamine (MtBN) was tested for carcinogenicity by s.c. injection in the Syrian golden hamster. No tumors were observed at 160, 80 or 40 mg/kg/week, in accord with Druckrey's report that ethyl-t-butylnitrosamine (EtBN), the homolog of MtBN, was not carcinogenic in the rat. Acetoxymethyl-t-butylnitrosamine, an activated form of MtBN, was also chronically tested by s.c. injection and found to be non-carcinogenic. It was demonstrated that 2-methylpropane diazotic acid, the proposed "ultimate" reactive metabolite of MtBN, afforded the carbenium ion product t-butyl alcohol in 63% yield. These results are consistent with the hypothesis that MtBN and EtBN are not carcinogenic because the proposed "ultimate" metabolite in their metabolic activation cannot interact with the critical cellular site due to steric reasons.

Animals↗
PubMed1981

The surface cell structure of oral carcinoma: a scanning electron microscope study of 32 cases.

Biopsies of 32 cases of oral carcinoma were studied by histology and by scanning electron microscopy. The surface morphology of the lining epithelium and of individual cells was often bizarre and showed varying differentiation; polymorphism was characteristic in both cell forms and sizes. These observations indicate that SEM may be helpful for the early diagnosis of changes in the oral mucosa. Findings were compared to the surface cell ultrastructure of oral benign and precancerous lesions.

Adult↗
PubMed1981

Inhalation studies with benzo[a]pyrene in Syrian golden hamsters.

Groups of Syrian golden hamsters were exposed by inhalation to benzo[a]pyrene (BP) in concentrations of 2.2, 9.5, and 45.6 mg/m3 air. Although 45.6 mg BP/m3 air was carcinogenic and toxic, 2.2 mg BP/m3 air led to no neoplastic response. The highest tumor incidence was seen in the group exposed to 9.5 mg BP/m3 air. Average survival times were similar in the controls (not exposed to BP) and in the 2 groups given 2.2 and 9.5 mg BP/m3 air. Exposure-related neoplasms were found in the nasal cavity, larynx, pharynx, esophagus, and forestomach. Bronchogenic tumors did not develop.

Administration, Intranasal↗
PubMed1981

Scanning electron microscopical investigations on the respiratory epithelium of the Syrian golden hamster III. Regeneration after traumatic injury.

To investigate the extent to which intratracheal intubation may alter the respiratory epithelium of the Syrian golden hamsters, single and repeated intubations were undertaken and the resulting injury and subsequent epithelial regeneration were examined by scanning electron microscopy. Generally, epithelial injury as a result of a single intubation had healed ad integrum within 20 to 40 days. On the other hand, repeated treatment often caused tracheitis and led to prolonged regeneration which sometimes persisted as papillary hyperplasia 40 days after the final intubation. The appropriateness of intratracheal instillation as a method of administering chemical carcinogens and the similarity of the epithelial regeneration processes to early neoplastic alterations of the epithelium are discussed.

Animals↗
PubMed1980

Characteristic molar ratios of magnesium, carbon dioxide, calcium and phosphorus in the mineralizing fracture callus and predentine.

From fracture callus in different stages of mineralization the contents of Mg, CO2, Ca and P were determined and compared with those found in predentine. It was found that the Mg- and CO2-contents are high in relation to Ca and P values during the prestages and early stages of mineralization. These relatively high Mg- and CO2-values are connected with high Mg/Ca, Mg/P, CO2/Ca and CO2/P ratios which strongly decrease with the increasing degree of mineralization. These results seem to be part of a general controlling mechanism of the calcification.

Animals↗
PubMed1980

Comparative study of the carcinogenic effect of BHP and BAP on NMRI mice.

The carcinogenic effects of N-bis(2-hydroxypropyl)nitrosamine (BHP) and N-bis(2-acetoxypropyl)nitrosamine (BAP) were studied in NMRI mice treated subcutaneously once weekly for life. The highest incidences of tumours were found in the lung (73-100%), in the liver (67-100%) and nasal cavity (0-33%) in both sexes of mice. Data were similar in animals treated with BHP or BAP. These tumours were adenomas, adenocarcinomas and squamous cell carcinomas (nasal cavity and lung) as well as hemangio-endotheliomas and hemangioendotheliosarcomas (liver). The lung tumours were found in the control mice (27-50%) 20 weeks later than in the experimental animals. The rate of malignant neoplasms rose with increasing survival and decreasing dose levels.

Animals↗
PubMed1980

The effects of cyclophosphamide, nitrosomethylurea and benzo(a)pyrene on the rat incisor.

Wistar rats given a single intraperitoneal injection of 75 mg cyclophosphamide revealed dental anomalies in the form of shortening or lengthening of incisors, and development of supernumerary teeth. Rats given additionally 5 mg/kg b. w. of a nitrosomethylurea solution over a period of four months showed the same dental anomalies, but with relatively shorter latency times. In a supplementary investigation examining the effects of benzo(a)pyrene and nitrosomethylurea applied locally to the organon dentale, neoplastic lesions and dental dysplasia were seen.

Animals↗
PubMed1980

[The effect of radionuclides on the rat masticatory organ].

The effects of incorporated radium nuclides were examined clinically, roentgenologically, histologically, gamma-spectrometrically, and autoradiographically in animal experiments. The experimentally induced resorption can be compared with alterations observed with man.

Animals↗