Search PubMed⌕ Search

Biomedical subjects

C Thomas

Publications and source records attributed to C Thomas.

At least 523 records · Page 29Linked to original sources
PubMed1978

Growth cone formation in cultures of sensory neurons.

Three experimental situations have been found in which cultured sensory neurons from embryonic chicken will form growth cones from positions along the length of the neurite. If the neurons are dissected with a remaining short axonal stump and plated into serum-free medium, they can form a morphologically normal growth cone from the stump within 15 min, even in the presence of cycloheximide or puromycin. When neurites growing in culture media with low levels of serum are cut at any point with microneedles, growth cones are produced quickly from the amputated stump, usually within 20 min. Treatment of growing neurons with low concentrations of colchicine, Colcemid, or podophyllotoxin results in the progressive appearance of lateral filopodia and regions of flattened cytoplasm that closely resemble growth cones except for their preterminal positions. These observations show that the potential to form growth cones is distributed throughout the neuron and suggest that this normally repressed in some way by the neuronal microtubules.

Axons↗
PubMed1978

Filtration rate and stop-flow pressure feedback responses to nephron perfusion in the dog.

Experiments were performed to evaluate the influence of the distal tubular feedback mechanism on glomerular function in the dog. Single nephron glomerular filtration rate (SNGFR) and stop-flow pressure (SFP) were measured from early segments of proximal tubules during alterations in distal perfusion rate (via a late proximal puncture site) and perfusate composition. Perfusion rate (PR) was varied from 16 to 68 nl/min with a microperfusion pump. The intermediate segment of the nephron was blocked with a solid wax cast, thus preventing retrograde influences of the microperfusion procedure. During perfusion with an ultrafiltrate of plasma and an artificial tubular fluid solution (ATF), SNGFR decreased from 63 +/- 2.6 (SE) nl/min at a PR of 16 nl/min to 20 +/- 2.4 nl/min at a PR of 63 +/- 2.6 nl/min. At a PR of 16 nl/min, SFP was 48 +/- 1.3 mmHg with ultrafiltrate and ATF. Increases in PR to 68 nl/min led to a reduction in SFP to 26 +/- 1.5 mmHg. SFP was also measured during changes in PR with various electrolyte solutions of decreasing complexity. Elimination or substitution of Na+, K+, Cl-, HCO3-, and Ca2+ did not significantly alter the magnitude of the feedback response to increases in PR to 68 nl/min. These results confirm the existence of a feedback system in the dog capable of adjusting glomerular function in response to changes in distal perfusion rate. The results based on the various perfusion solutions fail to indicate a unique requirement for any specific component.

Animals↗
PubMed1978

[Histopathological diagnosis in the animal experiment (author's transl)].

Spontaneous and experimentally induced organ alterations in laboratory animals do not always coincide with comparable lesions in human pathology. In addition, the discrimination between experimental tissue alterations and non-pathological structural variations may be difficult. In such cases a clear-cut separation can only be achieved by a proven dose-response relation, which, however, requires a quantitative or semiquantitative registration of histological findings.

Animals↗
PubMed1978

[Recent findings on the genealogy, clinical aspects and histology of a family with periodic hyperkalemic paralysis].

A family presenting a hyperkalemic form of periodic paralysis was studied through six generations; 31 individuals were affected, 14 could be examined. Periods of diffuse or localized muscle weakness, lasting one to four days, were associated with the classic adynamic attacks. Myotonic symptoms were discrete. Some patients, in particular the hard manual workers, exhibited a permanent proximal deficiency. Serum potassium level was in the lower normal range but raised during the attacks. EMG showed a polymorphic pattern, suggesting a functional neuro-muscular block. The histological and ultrastructural changes were pleiomorphic: vacuoles, tubular aggregates and fibers were found in a patient with permanent weakness; a pure type II fibre atrophy was noticed in another patient, without any weakness between the attakcs. Acetazolamide treatment gave good results in four cases out of seven.

Adolescent↗
PubMed1977

Autoregulation of nephron filtration rate in the dog assessed by indicator-dilution technique.

Micropuncture studies were conducted in anesthetized dogs to evaluate single nephron glomerular filtrate rate (SNGFR) and SNGFR autoregulation when assessed by means of an indicator-dilution technique (SNGFRID), which does not require interruption of distal volume delivery. In 18 dogs, control renal arterial pressure was 124 +/- 11 mmHg (SD), renal blood flow (RBF) was 185 +/- 58 ml/min, and whole kidney GRF was 37 +/- 7 ml/min. SNGFRID averaged 57 +/- 15 nl/min and was significantly lower than SNGFR determined on the basis of total collections (SNGFRTC) from proximal tubules (75 +/- 17 nl/min). However, SNGFRID was not significantly different from the overall average SNGFR of 62 +/- 12 nl/min estimated from whole kidney GFR and the total number of glomeruli (613,000 +/- 74,000). In 10 animals, renal arterial pressure was reduced to an average of 94 +/- 8 mmHg; whole kidney autoregulation was highly efficient and average RBF and GRF remained within 1 and 3% of their control values. Likewise, SNGFRID was not significantly altered at 52 +/- 17 and 52 +/- 16 nl/min. In contrast, SNGFRTC decreased significantly from 72 +/- 17 to 51 +/- 13 nl/min. These results indicate that the indicator-dilution technique provides a reliable assessment of SNGFR and allows the manifestation of single nephron autoregulatory behavior. They provide further support for the hypothesis that maintenance of distal volume delivery may be a necessary aspect of the autoregulation phenomenon.

Animals↗
PubMed1977

[The influence of renal artery occlusion on tumor growth of experimental nephroblastomas (author's transl)].

Nephroblastomas are induced in rats with N-Methyl-N-Nitroso-Urea, and selective renal artery occlusion is performed. This procedure has the same effect like occlusion by embolization. The effect of renal artery occlusion on the growth rate of nephroblastmas is controlled by angiography and gross and microscopic examinations up to 70 days following ischemia, the results are compared with a group of untreated nephroblastoma rats. There is a marked reduction of tumor size and a decrease in tumor proliferation. There is an immediate tumor cell death induced by acute and complete ischemia. Collateral blood vessels cause residual arterial blood supply of tumor parenchyma. There seems to be a correlation between collateral blood delivery and tumor size. Even 70 days after permanent ischemia there are areas of obviously absolute normal tumor cells. The conclusion of this experimental study demonstrated that growth rate of tumors can be reduced by ischemia although potentially malignancy still remains. Clinical embolization therapy is justified only in nonoperable patients with hypernephroma and with massive hematuria.

Animals↗