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Biomedical subjects

K Thayer

Publications and source records attributed to K Thayer.

5 recordsLinked to original sources
PubMed2001

Cell differentiation lineage in the prostate.

Prostatic epithelium consists mainly of luminal and basal cells, which are presumed to differentiate from common progenitor/stem cells. We hypothesize that progenitor/stem cells are highly concentrated in the embryonic urogenital sinus epithelium from which prostatic epithelial buds develop. We further hypothesize that these epithelial progenitor/stem cells are also present within the basal compartment of adult prostatic epithelium and that the spectrum of differentiation markers of embryonic and adult progenitor/stem cells will be similar. The present study demonstrates that the majority of cells in embryonic urogenital sinus epithelium and developing prostatic epithelium (rat, mouse, and human) co-expressed luminal cytokeratins 8 and 18 (CK8, CK18), the basal cell cytokeratins (CK14, CK5), p63, and the so-called transitional or intermediate cell markers, cytokeratin 19 (CK19) and glutathione-S-transferase-pi (GSTpi). The majority of luminal cells in adult rodent and human prostates only expressed luminal markers (CK8, CK18), while the basal epithelial cell compartment contained several distinct subpopulations. In the adult prostate, the predominant basal epithelial subpopulation expressed the classical basal cell markers (CK5, CK14, p63) as well as CK19 and GSTpi. However, a small fraction of adult prostatic basal epithelial cells co-expressed the full spectrum of basal and luminal epithelial cell markers (CK5, CK14, CK8, CK18, CK19, p63, GSTpi). This adult prostatic basal epithelial cell subpopulation, thus, exhibited a cell differentiation marker profile similar to that expressed in embryonic urogenital sinus epithelium. These rare adult prostatic basal epithelial cells are proposed to be the progenitor/stem cell population. Thus, we propose that at all stages (embryonic to adult) prostatic epithelial progenitor/stem cells maintain a differentiation marker profile similar to that of the original embryonic progenitor of the prostate, namely urogenital sinus epithelium. Adult progenitor/stem cells co-express both luminal cell, basal cell, and intermediate cell markers. These progenitor/stem cells differentiate into mature luminal cells by maintaining CK8 and CK18, and losing all other makers. Progenitor/stem cells also give rise to mature basal cells by maintaining CK5, CK14, p63, CK19, and GSTpi and losing K8 and K18. Thus, adult prostate basal and luminal cells are proposed to be derived from a common pleuripotent progenitor/stem cell in the basal compartment that maintains its embryonic profile of differentiation markers from embryonic to adult stages.

Animals↗
PubMed2001

Significant effects of mild endogenous hormonal changes in humans: considerations for low-dose testing.

We review the significant and adverse health effects that can occur with relatively small endogenous hormonal changes in pubertal and adult humans. We discuss the effects of hormonal changes that occur within normal physiologic ranges--such as the rising levels of estrogen in peripuberty, which cause growth spurts at low levels and then the fusion of epiphyses at higher levels--and the hormonal variations during the menstrual cycle and their relation to genital phenotypic changes and intercurrent disease evolution. We turn next to adaptive changes in gonadal and other functions during aging, exercise, stress, starvation, and chronic diseases, which can serve as models for the effects of exogenous, hormonally active compounds. Then we review the states of borderline hormonal imbalances such as subclinical (having few or very mild symptoms, if any) hypothyroidism or hyperthyroidism, glucose intolerance, and other endocrine conditions. Finally, we review the deleterious systemic effects of gonadal imbalance. Information stemming from clinical observations leads to the concept of "no threshold" within the endocrine system and thus illustrates the importance of considering low-dose testing for chemicals that interfere with hormonal activity. We also urge attention to more sensitive, less visible end points such as osteoporosis, increased risk for cardiovascular disease, or cognitive changes.

Adolescent↗
PubMed1999

Medically resistant neonatal hypertension: revisiting the surgical causes.

OBJECTIVE: To present the importance of searching for the surgical causes of pharmacologically resistant hypertension in the neonatal population. STUDY DESIGN: A case report and discussion are provided. RESULTS: Severe hypertension in the neonatal period is uncommon and almost always has a secondary cause. Although a majority of hypertensive neonates can be successfully managed with medical therapy, some cases are resistant to pharmacological treatment. We report three hypertensive neonates who failed to respond to intensive multidrug therapy. This led to further evaluation and identification of obstructive uropathies in two neonates and renovascular disease that necessitated surgical intervention. Subsequently, all patients had prompt resolution of hypertension and normalization of renal function. All are now off antihypertensive medications and have normal renal function at 12 months of follow-up. CONCLUSION: Our report exemplifies the importance of the consideration of surgical etiologies for differential diagnosis in neonates with severe hypertension that is unresponsive to pharmacological therapy. Early diagnosis and prudent management of these etiologies reduce morbidity and mortality and preserve of renal function.

Cystostomy↗
PubMed1998

Applications of the KTP laser in the treatment of posterior urethral valves, ureteroceles, and urethral strictures in the pediatric patient.

PURPOSE: We describes our experience using the potassium titanyl phosphate (KTP)-532 laser in treating posterior urethral valves, ureteroceles, and urethral strictures in the pediatric patient. METHODS: A retrospective chart review was performed from 1987 to 1997 on a total of 33 pediatric patients who underwent retrograde endoscopic treatment for posterior urethral valves (PUV), ureteroceles (UC), and urethral strictures using a KTP-532 laser. RESULTS: Overall, our success rate was excellent in the treatment of valves and ureteroceles. With a mean follow-up of three years in the PUV group, no urethral strictures of micturation abnormalities were seen. The majority of ureteroceles were decompressed and only half of our patients required and additional procedure. Our experience with urethral strictures, however, was not as promising. All of these patients ultimately required open urethral reconstruction. CONCLUSION: The desirable thermal characteristics of the KTP laser, along with minimal complications and the availability of delicate pediatric endoscopic instruments have made this operation optimally suited for treating posterior urethral valves and ureteroceles in infants. However, the advantages for treating urethral strictures in children with the laser still remains to be established.

Adolescent↗