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P M Mathisen

Publications and source records attributed to P M Mathisen.

5 recordsLinked to original sources
PubMed1989

Thyroid hormone induces constitutive keratin gene expression during Xenopus laevis development.

We have used in vitro explant cultures of Xenopus laevis skin to investigate the role that the thyroid hormone triiodothyronine (T3) plays in activating the 63-kilodalton (kDa) keratin genes. The activation of these genes in vivo requires two distinct steps, one independent of T3 and one dependent on T3. In this report we have shown that the same two steps are required to fully activate the 63-kDa keratin genes in skin explant cultures, and we have characterized the T3-mediated step in greater detail. Unlike the induction of transcription by T3 or steroid hormones in adult tissues, there was a long latent period of approximately 2 days between the addition of T3 to skin cultures and an increase in concentration of keratin mRNA. While the T3 induction of 63-kDa keratin gene transcription cannot occur until age 48, a short transient exposure of stage 40 skin cultures to T3 resulted in high-level expression of these genes 5 days later, when normal siblings had reached stage 48. This result indicates that T3 induces a stable change in epidermal cells which can be expressed much later, after extensive cell proliferation has occurred in the absence of T3. Once the 63-kDa keratin genes were induced, they were stably expressed, and by the end of metamorphosis T3 had no further effect on their expression. The results suggest that T3 induces constitutive expression of the 63-kDa keratin genes during metamorphosis.

Animals↗
PubMed1988

A comparison between haematological parameters in 'capillary' and venous blood from healthy adults.

In 40 healthy adult volunteers of both sexes blood samples were taken simultaneously from an antecubital vein in EDTA-Vacutainers and from a fingertip in EDTA-Microtainers. Haematological measurements were subsequently performed in an Ortho-ELT 800 WS analyzer. Significant differences were obtained between the two sets of samples. In accordance with current literature, the 'capillary' thrombocyte count was either identical to, or more frequently substantially lower than the corresponding venous count. On the contrary, the 'capillary' erythrocyte count and the haematocrit and haemoglobin values significantly exceeded those of venous blood, while the red cell indices MCV, MCH and MCHC were identical. The total leucocyte count was substantially elevated in 'capillary' blood compared with the corresponding venous samples. Moreover, the 'capillary' differential leucocyte counts showed elevations which directly reflected the various particles' size. Possible explanations of these findings are discussed.

Adult↗
PubMed1987

Thyroid hormone induction of keratin genes: a two-step activation of gene expression during development.

To determine the mechanism of action of the thyroid hormone triiodothyronine (T3) during metamorphosis of the amphibian epidermis, we have investigated the developmental activation of the 63-kD keratin genes in the frog Xenopus laevis. These genes code for three closely related keratins that first appear in the larval epidermis and accumulate during metamorphosis to become the most abundant proteins in the adult epidermis. We report here that the 63-kD keratins and their mRNAs first appear at stages 48-52. The level of 63-kD keratin gene expression remains relatively low until stage 56 and then increases dramatically. Quantitative analysis of the concentration of 63-kD keratin mRNA demonstrates low levels until stage 55/56, followed by an increase greater than 300-fold from stage 55/56 to the adult. Each adult cell contains approximately 55,000 molecules of the 63-kD keratin mRNAs. T3 is not required for the initial activation of the 63-kD keratin genes, but high-level expression is absolutely dependent on T3. High-level expression is prevented by propylthiouracil, which inhibits thyroid hormone synthesis and can be induced precociously both in vivo and in vitro with exogenous T3 as early as stage 48, but not prior to that time. Thus, the full activation of the 63-kD keratin genes during development requires two regulatory steps, one independent and one dependent on T3.

Animals↗
PubMed1985

Developmental changes in keratin patterns during epidermal maturation.

The biochemical maturation of the epidermis of Xenopus laevis was examined through an identification of the keratins expressed at selected stages of development. The keratin patterns obtained were compared to those observed in the adult epidermis and two Xenopus non-epidermal, epithelial cell lines. The keratins expressed during development can be grouped into three classes: (1) keratins which are restricted to the embryonic epidermis (58 and 59 kDa); (2) keratins which are prominent during development, but become minor components of the adult epidermis (47, 48, and 60 kDa); and (3) keratins which accumulate during development to become the major keratins of the adult epidermis (49, 53, 56, and 63 kDa). The embryo-specific keratins are present at all developmental stages prior to metamorphosis which we have investigated, but disappear when the epidermis keratinizes during metamorphosis. Both class 1 and 2 keratins, while undetectable or minor components of the adult skin, are present in the two non-epidermal cell lines. In contrast, the class 3 keratins show little overlap with the keratins of these cell lines. All of the class 3 keratins appear after hatching with the exception of the 53-kDa keratin which is present at the earliest developmental stage which we have examined. All of the major keratins of the adult epidermis accumulate as metamorphosis proceeds, while the embryo-restricted keratins are gradually lost.

Animals↗