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L Johnson

Publications and source records attributed to L Johnson.

At least 307 records · Page 17Linked to original sources
PubMed1989

Evaluation of the human testis and its age-related dysfunction.

The human testis has been evaluated by its endocrine function, daily sperm output in ejaculates, general appearance of seminiferous tubules, differential cell counts in the testis, and daily sperm production. Within-subject variation for total sperm count in ejaculates is extremely high at 42% to 75% coefficient variation. This variation can be reduced to 12% by averaging the counts obtained for the last three of five daily ejaculates. Plasma FSH concentrations are particularly useful in assessing the status of seminiferous epithelium and/or its Sertoli cell function in infertile men. In aged men, plasma LH, FSH, and estradiol concentrations are higher while plasma testosterone, free testosterone, and the ability of the testis to secrete testosterone following stimulation are reduced. Other age-related changes in human testes include a high incidence of azoospermia, reduced sexual activity, reduced testicular size, impaired spermatogenesis, reduced tubular length, increased thickness of tubular boundary tissue, sclerosis, focal mononuclear orchitis, and dilation of the rete testis. Due to the long duration of the spermatogenic cycle and low numbers of germ cells in human testis, daily sperm production per g parenchyma (efficiency of spermatogenesis) is much lower in humans than in other species. Testicular parenchymal weight, proportion of testis occupied by seminiferous epithelium, volume of seminiferous epithelium, and daily sperm production are significantly reduced in aged men. In various species, including man, germ cell degeneration occurs during spermatocytogenesis, meiosis, and/or spermiogenesis. Germ cell degeneration plays a pivotal role in spermatogenesis, but the mechanisms of degeneration, its etiology, and approaches for its prevention remain unclear.

Adult↗
PubMed1989

Natural killer cell activity is reduced in patients with severe forms of inherited epidermolysis bullosa.

Natural killer (NK) cell activity was evaluated in 34 patients with inherited forms of epidermolysis bullosa (EB). While the NK activity of EB simplex patients did not differ from that of control subjects, persons with more severe forms of EB demonstrated significant reductions in NK activity. The degree of this reduction was directly related to the severity of the skin involvement by EB with recessive dystrophic EB patients having the lowest NK activity. The absolute number of cells bearing NK surface markers in the peripheral blood of patients with recessive dystrophic EB did not differ from that of normal control subjects. This reduced NK activity may be at least partially responsible for the occurrence of septicemia in some persons with severe forms of EB and for the development of metastatic squamous cell carcinoma in patients with dystrophic EB.

Adult↗
PubMed1989

Blood vitamin and trace metal levels in epidermolysis bullosa.

Plasma or erythrocyte levels of ten nutrients (vitamins A, C, B12 and B6; folate; thiamine; riboflavin; zinc; copper; iron) were assayed in 73 patients with various forms of inherited epidermolysis bullosa (EB). Whereas the mean level for each nutrient was within its normal range, deficient levels were noted in individual EB subsets for selected nutrients. Notable abnormalities included low levels of plasma iron and zinc (in junctional EB and recessive dystrophic EB), vitamin C (primarily in EB simplex), vitamin A (in junctional and recessive dystrophic EB), vitamin B12 (primarily in EB simplex), and vitamin B6 (especially in recessive dystrophic EB). With the exception of low plasma iron and zinc levels in junctional and recessive dystrophic EB, however, only a minority of patients in any of the EB subsets had low levels of most of the other nutrients, and an apparent correlation with malabsorption was possible with only selected nutrients.

Adolescent↗
PubMed1988

Primary and secondary structural determinants in the receptor binding sequence beta-(38-57) from human luteinizing hormone.

The intercysteine "loop" sequence 38-57 in the beta subunit has been shown to be a determinant for expression of biological activity in human lutropin (hLH) and choriogonadotropin (hCG) [Keutmann, H. T., Charlesworth, M. C., Mason, K. A., Ostrea, T., Johnson, L., & Ryan, R. J. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 2038]. Together with other sequences, the 38-57 region may contribute to a multicomponent receptor binding domain in hLH/hCG. Because the structural features influencing activity in this important region are not easy to evaluate in the full-length subunit, we have used analogues of hLH beta-(38-57) prepared by solid-phase synthesis. The peptides were tested for inhibition of 125I-labeled hCG binding to rat ovarian membrane receptors. Secondary structure was analyzed by circular dichroism (CD) and by reactivity with antibodies to the native 38-57 peptide. An analogue lacking the 38-57 disulfide linkage retained 20% receptor binding and full immunoreactivity. "Far"-ultraviolet CD profiles were essentially identical with those of the disulfide-intact peptide; a transition from 10% to 30% alpha-helix in 90% trifluoroethanol was characteristic of both. The peptide thus appears not to require the disulfide bridge to retain a looped conformation with amphipathic secondary structure. An essential positive charge at position 43 was shown by complete loss of activity upon substitution of Asp or Ala for the Arg found in all known species of LH. Other analogues showed a requirement for a neutral residue at position 47, also highly conserved.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1988

Prenatal testing for Duchenne and Becker muscular dystrophy.

DNA studies were undertaken following 53 requests from pregnant women at risk for Duchenne and Becker muscular dystrophy, including 32 in whom there was only 1 affected individual in the family (sporadic cases). The DNA restriction fragment length polymorphisms were informative in 51 of the 53 cases. In 10 of 25 pregnancies with male fetuses the risk to the fetus was reduced to 5% or less. Referral of possible carriers before onset of pregnancy is strongly advisable on both medical and economic grounds. The banking of DNA from affected individuals for future use in the estimation of risks to their relatives should be encouraged.

Carrier State↗
PubMed1988

Mouse exophthalmic chronic orbital inflammatory disease. Induction by human leucocyte intracellular Mollicutes.

Mollicutes are cell wall deficient bacteria which may be overlooked or confused with viruses because of indistinct light microscopic morphology, poor staining, difficulty in cultivation, and the ability to pass 0.450 micron filters. As they have a distinctive ultrastructural appearance they can be identified using transmission electron microscopy [TEM]. Using TEM vitreous leucocytes from chronic endogenous uveitis patients may demonstrate non-cultivable intracellular 0.005-1.0 micron mollicute-like organisms [MLO], some of which develop into distinctive cell walled cocci, 0.5-0.7 micron in diameter. Inoculation of those MLO containing human vitreous into mouse eyelids produces chronic cardiac and uveal vasculitis with orbital inflammation. Similar MLO are found within the mouse lesional leucocytes. This report describes the chronic orbital inflammation with vasculitis in 67 of 100 of those MLO inoculated mice versus 0 of 200 controls (P less than 0.05). Exophthalmos with inflammation also occurred in 12 of those 67 mice (P less than 0.05). MLO were found within orbital lesional leucocytes of 10 of 10 of those mice using a TEM versus 0 of 10 controls. The results indicate that vasculitis and exophthalmos were important features of this MLO induced mouse orbital inflammation. The implication of these results for human idiopathic chronic orbital inflammatory disease is discussed.

Animals↗
PubMed1988

Development of a translating bed for total body irradiation.

Total body irradiation is used to prepare a patient for bone marrow transplantation. Traditional techniques often sacrifice dose uniformity for patient comfort and ease of treatment. A method has been developed using a translational bed under a Cobalt 60 photon beam. The bed and controller were designed and built on site. A bolused patient lying in the bed is moved at constant speed through the beam. Using this technique, dose homogeneity is optimized by the use of bolus, extended source-skin distance, adequate field size and use of anterior/posterior fields. The dose rate represents a compromise between a value high enough to keep treatment times tolerable by the patient and one that is sufficiently low to avoid treatment complications. The value of 50 cGy/min which was used meets these requirements. Extensive phantom measurements have shown that the dose homogeneity can be obtained to within an acceptable limit of +/- 5%.

Beds↗
PubMed1988

Effect of age on the composition of seminiferous tubular boundary tissue and on the volume of each component in humans.

Seminiferous tubular boundary tissue thickens with age. The objective was to characterize the composition of boundary tissue in 16 young adult (20 to 29 years) and 18 older adult (51 to 84 years) men. Testes were perfused with glutaraldehyde, placed in osmium, and embedded in Epon 812 (Ladd Research Industries, Burlington, VT). Paired testicular weight, length of tubules, volume of seminiferous epithelium, and daily sperm production were significantly reduced in older men. Although the thickness of boundary tissue was greater (P less than 0.01) in older men, the volume of boundary tissue per man was similar between age groups. The percentages and volumes per man of boundary tissue myoid cells, collagen, microfibrils, and other components also were similar (P greater than 0.05) between age groups. This study confirms that age-related thickening of boundary tissue occurs without the new deposition (augmentation) of collagen or other extracellular components.

Actin Cytoskeleton↗
PubMed1988

Effect of daily spermatozoan production but not age on transit time of spermatozoa through the human epididymis.

Daily spermatozoan production, numbers of epididymal spermatozoa, and transit times of spermatozoa through different regions of the epididymis were determined in 38 men, aged 20-49 or 50-79 yr. Specimens were obtained at autopsy within 24 h of death due to traumatic injury or heart failure. Subjects were in apparent good health prior to death, and death was not preceded by an extended period of hospitalization. Daily spermatozoan production per testis (DSP/T) and numbers of epididymal spermatozoa were determined from counts of maturation-phase spermatids or epididymal spermatozoa in tissue homogenized in a Waring blender. Epididymal transit time was calculated as the number of spermatozoa in a given region of the epididymis or in the entire epididymis divided by DSP/T of the connected testis. Parenchymal weight, spermatozoan production rate, numbers of epididymal spermatozoa, and epididymal transit time were similar (p greater than 0.05) between paired testes or epididymides. Men were divided into four groups on the basis of age and DSP/T. Since there was no (p greater than 0.05) effect of age on epididymal transit time, men in different age groups were combined within their respective group on the basis of DSP/T. In the group with high DSP/T, DSP/g parenchyma was much higher and epididymal transit time was much faster. However, parenchymal weights and numbers of epididymal spermatozoa were similar (p greater than 0.05) between DSP/T groups. The similarity in number of spermatozoa in epididymides of men whose DSP/T differed by threefold is consistent with the inability of the human epididymis to store many spermatozoa when no blockage is present.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Osmolality--limits of physical tests.

The use of physical methods such as freezing point depression for the estimation of osmolality of preparations given to infants may be misleading. The reasons for this are discussed, and reference made to some other properties of preparation vehicles which may be of concern.

Animals↗
PubMed1988

Evaluation of the efficacy of topical bufexamac in epidermolysis bullosa simplex. A double-blind placebo-controlled crossover trial.

Although, as yet, there is no specific treatment of epidermolysis bullosa (EB) simplex, anecdotal reports suggest the possible efficacy of one of the newer topical nonsteroidal anti-inflammatory agents, bufexamac. To determine whether bufexamac has any role in the management of this disease, a double-blind placebo-controlled crossover clinical trial was undertaken with ten patients (nine, Weber-Cockayne variant; one, generalized EB simplex). Each of the two preparations was applied four times daily during the 2 four-week treatment periods. Weekly assessments included counts of blisters, crusts, and erosions, and assessments of alterations in cutaneous pain, healing times, and activity times before further blister formation. Although considerable variability in individual responses was noted, no significant difference was detectable between the active drug and its matched placebo. On the basis of these findings, it was concluded that 5% topical bufexamac is ineffective in the treatment of EB simplex.

Administration, Cutaneous↗
PubMed1988

Mouse lethal cardiovascular disease: induction by human leucocyte intracellular Mollicutes.

Plant pathologists have known for several years that intracellular Mollicutes (M), i.e. cell wall deficient bacteria, are plant vascular pathogens, but because those M are non-cultivatable, they can only be studied by Transmission Electron Microscopy (TEM). Only recently have similar M been shown to be human and animal pathogens. Those human ocular Vasculitis (V) and mouse chronic ocular and lethal systemic V producing M parasitize vitreous polymorphonuclear leucocytes, lymphocytes, and monocytes as 'viral-like' 0.005-0.010 micron elemental particles which grow within the leucocyte into 0.01-0.03 micron diameter tubules, 0.3-1.5 micron spherules, and distinctive 0.5-0.7 micron cocci with spore-like cell walls. This report describes the 48 arteriolar and capillary sized V, Aschoff nodules, valvulitis, and myocytolytic lesions in the heart and great vessels in 18 of 100 human vitreous VM containing eyelid inoculated mice versus 0 of 200 controls (P less than 0.05) plus VM within parasitized leucocytes in 15 of 15 of those lesions by TEM. The results indicate dissemination of VM from the eyelid to produce a significant incidence of distinctive multifocal VM directly induced cardiovascular micro-V lesions that probably contributed to their excessive mortality. Because several human idiopathic diseases develop similar cardiovascular lesions a TEM search for VM parasitized leucocytes in those human diseases seems justified.

Animals↗