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Biomedical subjects

L Johnson

Publications and source records attributed to L Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1996

Pain responses of hospitalized infants and children to venipuncture and intravenous cannulation.

The purpose of this study was to describe the experience of pain in infants and children in response to venipuncture and intravenous cannulation. Data on physiological, behavioral, and subjective responses were collected from 90 infants and children, in subgroups of 1 to 12 months, 1 to 3 years, 4 to 6 years, and 7 to 12 years. Changes in behavior were significant in all four groups, although the toddler group was the only group that showed a significant physiological change. The subjective measures showed that the children were able to identify their pain sites and intensity.

Age Factors↗
PubMed1996

Increased expression of xanthine oxidase and insulin-like growth factor I (IGF-I) immunoreactivity in skeletal muscle after strenuous exercise in humans.

The present study investigated the effect of 7 days of strenuous exercise on the quantity of xanthine oxidase and IGF-I in muscle. Fifteen male military trainees performed 1 week of terrain marching and warfare exercises. Muscle biopsies and blood samples were obtained prior to and after the week. After the week, the number of xanthine oxidase immunoreactive cells, identified as capillary endothelial cells and leucocytes, and the number of IGF-I immunoreactive cells, mainly vascular cells but also cells tentatively identified as satellite cells, were higher in the muscle (P < 0.05). Plasma creatine kinase activity was 650% higher after the week (P < 0.001) and the muscle content of hydroxyproline was elevated by 160% 2 months post-exercise (P < 0.05), both findings implying injury to the muscle. The present data provide a first observation of an elevated level of xanthine oxidase and IGF-I in human skeletal muscle after exercise. It is proposed that both substances increased as a result of cellular damage: xanthine oxidase because of the influence of immunomodulators, and IGF-I in association with regenerative processes. The increased expression of IGF-I in the muscle could, however, also reflect cellular growth in response to an elevated load on the muscle and the vascular bed.

Adult↗
PubMed1996

Body fat distribution and non-insulin-dependent diabetes: comparison of a fiber-rich, high-carbohydrate, low-fat (23%) diet and a 35% fat diet high in monounsaturated fat.

The effects of a fiber-rich, high-carbohydrate, low-fat (HCLF) diet and a modified-fat (MF) diet high in monounsaturated fat on body fat distribution were examined by dual-energy X-ray absorptiometry (DXA) in 16 subjects with non-insulin-dependent diabetes (NIDDM) during a randomized crossover study. Subjects lost similar amounts of body fat consuming the HCLF and MF diets (-0.83 +/- 0.37 and -0.87 +/- 0.40 kg, respectively) despite a marked difference in total fat consumption. With the MF diet, the ratio of upper- to lower-body fat (UF:LF) remained unchanged because fat was lost proportionately from the upper and lower body. In contrast, with the HCLF diet, a disproportionate loss of lower-body fat caused the UF:LF to increase. The effects of diet on regional body fat loss were significant (P < 0.05, two-factor repeated-measures ANOVA).

Absorptiometry, Photon↗
PubMed1996

Effect of developmental age or time after transplantation on Sertoli cell number and testicular size in inbred Fischer rats.

The objectives were to establish the developmental age of Fischer rats at which the Sertoli cell number is stabilized, to establish the normal reference plateau number of Sertoli cells for evaluation of testes after transplantation, and to determine whether the developmental pattern establishing Sertoli cell proliferation and stability are similar between intact and transplanted testes. Sertoli cell number was determined at ages 1--120 days in intact rats and at various times (10-90 days) after transplantation of prenatal or neonatal tests. Tests were fixed by vascular perfusion or by immersion with 2% glutaraldehyde and and immersion in 1% osmium and were embedded in Epon 812. Sections and serial sections were cut at 0.5 micrometer to determine the Sertoli cell nuclei volume density and the volume of an individual Sertoli cell nucleus by brightfield microscopy or at 20 micrometers to determine the maximum height and width of nuclei. A correction factor was calculated for intact (0.663 +/- 0.025) or for transplanted (0.558 +/- 0.029) testes to determine the volume of a single Sertoli cell nucleus from height and width measurements. In intact testes, Sertoli cell numbers significantly increased to Day 20 but were not different between 15 and 90 days. Sertoli cell number in prenatal or neonatal transplanted testes increased to 20 or 30 days posttransplantation and then stabilized to Day 60 or 90. There was no difference in the plateau number of Sertoli cells per rat between prenatal and neonatal testes. Sertoli cells in 10-day- and 30-day-transplanted testes incorporated 3H-thymidine when placed in culture. A few tubules had complete spermatogenesis at 90 days posttransplantation, indicating that Sertoli cells in some of these tubules were functional. Leydig cell structure appeared to be normal. Leukocytic infiltration of testes was not observed in intact rats or in rats receiving neonatal testes. Although transplanted testes showed a delay in reaching the plateau value for Sertoli cell number per testis and although the value reached was lower, the developmental pattern of Sertoli cell proliferation in transplanted testes was similar to that in intact rats.

Aging↗
PubMed1996

Effect of hypophysectomy, sex of host, and/or number of transplanted testes on Sertoli cell number and testicular size of syngeneic testicular grafts in Fischer rats.

One or more neonatal testicular grafts were transplanted for 60-65 days into young adult inbred Fischer rats to determine the effect of hypophysectomy, sex of host, and/or the number of transplanted testes on testicular size and Sertoli cell number. All host rats had been castrated or ovariectomized and some were hypophysectomized as well. At the end of the treatment, testes were fixed and embedded in Epon before histologic sections (0.5 micrometer or 20 micrometers) were evaluated by stereology. Testicular grafts placed in castrated adult male rats with intact pituitaries weighed more (p < 0.01) and had more (p < 0.01) Sertoli cells than those placed in hypophysectomized hosts. Testicular grafts that were recovered from hypophysectomized rats 34 days posttransplantation and placed in pituitary-intact males for 30 day had larger (p < 0.05) parenchymal weights and more Sertoli cells than did testes re-transplanted into hypophysectomized rats. However, this delayed period of Sertoli cell proliferation id not extend to 65 days of hypophysectomy. When two or four testes were transplanted into castrated males or ovariectomized female hosts for 65 days, there was no difference in the graft weights or Sertoli cell numbers between sexes. Four transplanted testes per rat produced more (p < 0.01) total testicular parenchyma and a greater (p < 0.01) number of Sertoli cells per testis than did two tests regardless of sex of the host. This model has shown that the period of Sertoli cell proliferation can be delayed by hypophysectomy, that Sertoli cell number can be influenced by endogenous hormones, and that a major component in regulation of testicular size is at the level of the testis in this model. Hence, this model should facilitate study of experimental endocrine manipulation control and potential experimental intervention to increase Sertoli cell number and testicular size.

Animals↗
PubMed1996

MAG3 renal transplant tomography SPECT with a non-SPECT agent.

The authors encountered a renal transplant patient in whom tubular stasis permitted sufficient time to perform SPECT using Tc-99m MAG3. SPECT revealed a defect that was not apparent on the planar study. Renal biopsy showed acute vascular rejection. On a subsequent Tc-99m MAG3 SPECT study the defect had resolved.

Adult↗
PubMed1996

Number and function of Sertoli cells, number and yield of spermatogonia, and daily sperm production in three breeds of boar.

The objective of this study was to determine the number of Sertoli cells per boar, daily sperm production, and germ cell yield per type A spermatogonium in mature Whitecross, Meishan, and West African boars. The paired parenchymal mass was greatest in the Whitecross boars and greater in Meishan than in West African boars. Daily sperm production per boar (x 10(9)) differed significantly (P < 0.05) among breeds (Whitecross: 12.5 +/- 1.5; Meishan: 6.0 +/- 0.5; West African: 2.9 +/- 0.3). Daily sperm production per boar was positively (P < 0.01) correlated with parenchymal mass (r = 0.97), number of A spermatogonia per testis (r = 0.88), and Sertoli cells per testis (r = 0.87). Daily sperm production per gram of testis was similar among breeds. Number of Sertoli cells and number of type A spermatogonia per boar were greater for the Whitecross but similar in the Meishan and West African boars. The number of Stage VII germ cells per Sertoli cell was greater (P < 0.05) in the Meishan (39.08 +/- 5.07), but similar in the Whitecross (19.91 +/- 1.62) and West African boars (15.81 +/- 2.43). The number of type A spermatogonia per testis was highly and positively (P < 0.01) correlated with number of Sertoli cells per testis (r = 0.95), and parenchymal mass (r = 0.88). There was a trend for the spermatid yield per type A spermatogonium to be greater in the Meishan boars, and this ratio was positively correlated with spermatid:Sertoli cell ratio (r = 0.62) but not with daily sperm production per boar or Sertoli cells per testis. No significant germ cell degeneration occurred during the long meiotic prophase, but the loss of progeny during postprophase of meiosis averaged 32.62% across all breeds. Germ cell degeneration was similar (P > 0.05) across breeds during spermiogenesis, and on average amounted to 8.6%. The increased number of type A spermatogonia and of Sertoli cells associated with larger testes for the Whitecross over West African or Meishan boars is sufficient to explain the higher sperm production in the Whitecross. However, the lower index of degeneration and more efficient Sertoli cell function in Meishan boars results in the daily sperm production being intermediate between that of the Whitecross and West African boars.

Africa↗
PubMed1996

Tandem high-dose chemotherapy supported by hematopoietic progenitor cells yields prolonged survival in stage IV breast cancer.

The aim of this phase II study was to determine the feasibility of using two (tandem) courses of high-dose alkylating agents with bone marrow or peripheral blood progenitor cell support in women with stage IV breast cancer. Women with stage IV breast cancer who had achieved a CR or PR during conventional chemotherapy were enrolled in a phase II trial of high-dose cyclophosphamide 7500 mg/m2 and thiotepa 675 mg/m2 (C+T) followed within 180 days by high-dose melphalan (M) 140 mg/m2. Bone marrow and/or GM-CSF mobilized peripheral blood hematopoietic progenitor cells were used to support high-dose C+T and high-dose M. Twenty-seven women were enrolled in this trial. The median age was 45 years (range 32-56). The median PS was 0 and all patients had achieved either a CR (4/27, 15%) or PR (23/27, 85%) to conventional chemotherapy. All 27 women underwent high dose C+T. The predominant toxicities were mucositis (81%), and diarrhea (81%); two patients (7%) died from infectious complications. Following C+T, the median time to hematologic recovery for neutrophils (ANC > 500 cells/mu 1) was 12 days and for platelets (>20 000 cell/mu 1), 23 days. Following C+T, 18 of 22 patients received high dose M; the predominant toxicities were nausea, vomiting (70%), and mucositis (91%). The median time to hematologic recovery for the ANC was 13 days and for platelets, 18 days. The overall response after high dose C+T and high dose M was 67% (CR, 15/27 patients (56%) and PR* (complete resolution of all measurable disease but persistent lytic disease or positive bone scan) 3/27 patients (11%). With median follow-up of 24 months, the actuarial freedom from relapse or treatment failure is 56% at 24 months. At 30 months 56% of patients are alive. For patients who achieve a CR or PR* the actuarial freedom from relapse or treatment failure at 24 months is 88%. In women with stage IV breast cancer who attain a CR or PR to conventional chemotherapy, tandem high-dose chemotherapy with ABMT can lead to prolonged relapse-free survival.

Adult↗
PubMed1996

A phase II study of cyclophosphamide followed by PIXY321 as a means of mobilizing peripheral blood hematopoietic progenitor cells.

Fourteen patients with stage II-IV breast cancer were enrolled in a phase II study of cyclophosphamide followed by PIXY321 as a means of mobilizing peripheral blood progenitor cells (PBPC). All 14 women tolerated PIXY321 well, with the predominant toxicities being erythema at the injection site, fever, and arthralgias. A median of two aphereses yielded a mean of 1.3 x 10(8) mononuclear cells/kg, 8.9 x 10(4) colony-forming units-granulocyte/macrophage (CFU-GM)/kg, and 4.5 x 10(6) CD34+ cells/kg. All 14 patients underwent high-dose chemotherapy with PBPC support, the median day to ANC >500 cells/microliter was 10.6, and the median day to platelets >20,000 cells/microliter was 13. The day of 90th percentile platelet recovery was 15. When compared to PBPCs mobilized by cyclophosphamide followed by GM-CSF, the use of PIXY321 may confer an advantage of enhanced platelet recovery.

Adult↗
PubMed1996

Nasogastric tube feeding in infants on peritoneal dialysis.

Enteral nutritional support is an important component of the care provided to infants receiving long-term peritoneal dialysis. In the majority of published experiences on this subject, the use of the nasogastric tube has facilitated the provision of required calorie and protein intake and resulted in an improved patient outcome. Advantages of the nasogastric route of nutritional support include the ease of administration, while recurrent emesis remains the most troublesome and frequent short-term complication associated with its use. Impaired oral-motor development may also result from nonoral feeding and should be addressed throughout the course of tube feeding.

Combined Modality Therapy↗
PubMed1995

In vivo MRI visualization of acute myocardial ischemia and reperfusion in ferrets by the persistent action of the contrast agent Gd (BME-DTTA).

BACKGROUND: Contrast agent-enhanced magnetic resonance imaging (MRI) has the potential to visualize myocardial ischemia. To date, however, no agent has been found that has a sustained effect that allows MRI detection for the entire duration of ischemia and reperfusion and thus is useful in conjunction with stress test MRI. In this article, we introduce the gadolinium complex of N3,N6-bis(2'-myrisotyloxyethyl)-1,8-dioxo-triethylene- tetraamine-N,N,N1,N1-tetraacetic acid [Gd(BME-DTTA)], an agent potentially useful for such a purpose. METHODS AND RESULTS: Four protocols were carried out. ECG-triggered, partially T1-weighted, spin-echo MRI was used in protocols A through C. In protocol A, in nonischemic ferrets, 50 mumol/kg Gd(BME-DTTA) induced a 70 +/- 5% intensity enhancement lasting 3 hours. In protocol B, the left anterior descending coronary artery was occluded, and a 99mTc-sestamibi-induced autoradiographic contrast verified (r = .87, P < .01) a Gd(BME-DTTA)-induced (n = 5) or Gd(DTPA)-induced (n = 4) MRI contrast. In the Gd(BME-DTTA) group a sustained contrast and in the Gd(DTPA) group a short-lived contrast were observed. In protocol C (n = 11), during ischemia, a 31 +/- 3.3% (P < .02) contrast was evident between the ischemic and nonischemic myocardial regions. Upon reperfusion, a contrast of 19 +/- 3% (P < .05) and 13 +/- 4.5% (P < .05) persisted for 5 and 15 minutes, respectively. Beyond 15 minutes, the contrast continued to diminish gradually. Nonradioactive microspheres verified (r = .87, P < .05) ischemia and reperfusion in this model. In protocol D (n = 4), blood delta R1 data showed that the blood pool retained Gd(BME-DTTA) for the entire time frame of the experiment at high enough concentration to provide an appropriate wash-in effect during the initial contrast enhancement and during reperfusion. CONCLUSIONS: This study demonstrates that Gd(BME-DTTA) induces a sustained MRI contrast between regions of normal versus ischemic myocardium, showing the potential of this agent for the diagnosis of ischemic heart disease in conjunction with stress tests.

Animals↗
PubMed1995

Efficiency of spermatogenesis.

Spermatogenesis is a process of division and differentiation by which spermatozoa are produced in seminiferous tubules. A measure of efficiency of spermatogenesis is the estimated number of spermatozoa produced per day per gram of testicular parenchyma. This measure is not influenced by species differences in testicular size; however, it is influenced by species differences in the numerical density of germ cells and in the life spans of these cells. Seminiferous tubules are composed of somatic cells (myoid cells and Sertoli cells), and germ cells (spermatogonia, spermatocytes, and spermatids). Activity of these three germ cells divide spermatogenesis into spermatocytogenesis, meiosis, and spermiogenesis, respectively. Spermatocytegenesis involves mitotic cell division to increase the yield of spermatogenesis and to produce stem cells and primary spermatocytes. Meiosis involves duplication and exchange of genetic material and two cell divisions that reduce the chromosome number and yield four spermatids. Spermiogenesis is the differentiation of spherical spermatids into mature spermatids which are released at the luminal free surface as spermatozoa. The spermatogenic cycle is superimposed on the three major divisions of spermatogenesis. Spermatogenesis and germ cell degeneration can be quantified from numbers of germ cells in various steps of development throughout spermatogenesis, and quantitative measures are related to number of spermatozoa in the ejaculate. Germ cell degeneration occurs throughout spermatogenesis; however, the greatest impact occurs during spermatocytogenesis and meiosis. Efficiency of spermatogenesis is related to the amount of germ cell degeneration, pubertal development, season of the year, and aging of humans and animals. Number of Sertoli cells and amount of smooth endoplasmic reticulum of Leydig cells (but not Leydig cell number) are related to efficiency of spermatogenesis. In humans, efficiency of spermatogenesis is reflected in number of spermatogenic stages per cross-section and number of missing generations within each stage; however, the arrangement of stages along the tubular length does not reflect differences in the efficiency of spermatogenesis. In short, spermatogenesis involves both mitotic and meiotic cell divisions and an unsurpassed example of cell differentiation in the production of the spermatozoon, and daily sperm production per g parenchyma is a measure of its efficiency.

Aging↗
PubMed1995

Structural analysis of human and murine flt3 ligand genomic loci.

Both the murine and human genomic loci that encode flt3 ligand have been cloned. flt3 ligand is a hematopoietic growth factor that stimulates the proliferation of stem and progenitor cells. The portions of the murine and human flt3 ligand genomic loci encompassing the coding region of the protein are approximately 4.0 kb and 5.9 kb, respectively. The human genomic locus is larger as a result of the presence of repeated sequences within introns I, II, IV, V and VI. The transmembrane isoform of the murine and human flt3 ligand proteins are each encoded within seven exons (1-5 + 7 and 8). Analyses of flt3 ligand cDNA clones show that alternative splicing of a putative sixth exon results in the generation of a soluble form of the flt3 ligand protein. The sizes of each of the exons are well conserved between species. Murine and human flt3 genomic loci have a similar exon: intron structure compared to the genomic loci encoding Steel factor and colony stimulating factor 1. These proteins, which appear to be ancestrally related, are hematopoietic growth factors that stimulate cells via specific and structurally related tyrosine kinase receptors on the cell surface.

Alternative Splicing↗