PubMed Health⌕ Search

Biomedical subjects

L Johnson

Publications and source records attributed to L Johnson.

At least 397 records · Page 22Linked to original sources
PubMed1984

Isolation of Chlamydia using McCoy cells and Buffalo green monkey cells.

Unselected eye and genital specimens from 233 patients were cultured for Chlamydia. The isolation rates were compared using McCoy cells and Buffalo green monkey cells, both procedures being performed with and without the addition of cycloheximide and centrifugation. No significant difference was found in the isolation rates using the four methods. The characteristics of the two cell lines and the advantages of omitting cycloheximide treatment and centrifugation are discussed.

Animals↗
PubMed1984

Leydig cell numbers, daily sperm production, and serum gonadotropin levels in aging men.

Age-related changes in Leydig cell number, daily sperm production, and circulating hormone levels were studied in 15 men between 20 and 48 yr of age and 15 men between 50 and 76 yr of age. Testes and blood samples were obtained at autopsy less than 15 h after death due to trauma or heart attack. Leydig cell number was determined by quantitative histometric estimation of the proportion of glutaraldehyde-perfused, decapsulated testicular parenchyma occupied by Leydig cell nuclei of measured average volume in both testes of each subject. Daily sperm production was determined by phase contrast cytometry of round spermatid nuclei in homogenates of both fixed testes from each individual. LH, FSH, PRL, and testosterone in serum from the heart or large veins were quantified by RIA. No relationship was detected between any of the testicular or hormonal values and postmortem time. The average total number of Leydig cells was reduced by 44% in the older men and was negatively correlated with age (p = -0.62) in all men. Mean serum LH was elevated more than 2-fold in the older men and was positively correlated with age (p = +0.53) in all men. Neither serum testosterone nor serum PRL changed significantly with age. Daily sperm production was more than 50% lower in older men and was negatively correlated with age (p = -0.76) in all men. Serum FSH was more than 3-fold higher in the older men and was positively correlated with age (p = +0.72) in all men. The highest FSH levels were found in men with the lowest rates of sperm production, and FSH and daily sperm production were inversely correlated even after the effects of age were removed. These findings show that the response of the human testis to aging is variable and that the predictive value of age for most testicular characteristics is weak at the level of individual men. Nevertheless, age accounts for more than a third of the variation in Leydig cell number, and it explains more than half the variation in daily sperm production. Hence, age is the largest single contributing factor yet identified in the search for explanations underlying the variation in testicular structure and function found in groups of normal men.

Adult↗
PubMed1984

Influence of age on sperm production and testicular weights in men.

Age-related changes in daily sperm production (DSP) and testicular weights were investigated in paired testes from 89 men aged 21-50 years and 43 men aged 51-80 years. For both DSP/testis and DSP/g parenchyma, remarkably large standard deviations exceeded 50% of mean values. However, DSP/g and DSP/testis for both right and left testes were approximately 30% higher in the younger than in the older group (P less than 0.01) and were negatively correlated with age (P less than 0.01) when data from both groups were pooled. Weights of whole testes and of testicular parenchyma were similar in both age groups and were not significantly correlated with age. However, testicular tunic weights were 29% higher in the older group (P less than 0.001) and were positively correlated with age (P less than 0.001). Both testicular tunic weight and the % of total testis occupied by tunic were negatively correlated with DSP/g (P less than 0.01); these correlations were weakened by removing the effect of age. Although total testicular weight and testicular parenchymal weight did not change with age, these values were about 10% lower on the left than on the right (P less than 0.001). In addition to its increase with age, testicular tunic weight was about 8% greater for right than for left testes in all men (P less than 0.001). Although the average size of the testis varied from right to left, DSP/g was similar in paired testes (P = 0.15), and the correlation between right and left DSP/g was high (rho = +0.89, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Effect of 5'-methylthioadenosine (a naturally occurring nucleoside) on murine hematopoiesis.

5'-Methylthioadenosine (MTA), a naturally occurring nucleoside, inhibited in vitro colony formation by murine erythroid (CFU-E) and granulocyte-macrophage (CFU-GM) progenitor cells in a dose-dependent fashion with maximal inhibition at concentrations of 2 X 10(-3) M and 1 X 10(-4) M, respectively. The inhibitory effect was reversible after up to 8 h of exposure to MTA but was irreversible after 24 h. MTA also inhibited hematopoietic progenitors in vivo. In mice given daily intraperitoneal injections of MTA for 28 days, CFU-GM were maximally reduced on day 14 to 51% of control. CFU-GM returned toward control levels by day 28 despite the continued administration of MTA. Hematocrit and leukocyte count were not reduced until day 28 and then only to 90% and 70% of control, respectively. MTA reached peak plasma levels of 2.8 X 10(-5) M 5 min after a single intraperitoneal injection of 75 mg/kg and was almost completely cleared by 60 min. These findings indicate that MTA produces reversible inhibition of murine hematopoietic progenitors both in vitro and in vivo. Despite the inhibitory effect on progenitors there is little effect on peripheral blood counts, which suggests that MTA inhibits hematopoietic proliferation without affecting hematopoietic differentiation.

Adenosine↗
PubMed1983

Testicular function of rats following exposure to microwave radiation.

Male Sprague-Dawley rats were exposed for 6 h per day for nine days to pulse-modulated microwave radiation (1.3 GHz, at 1-microseconds pulse width, 600 pulses per second). Exposures were carried out in cylindrical waveguide sections at a mean dose rate of 6.3 mW/g; sham controls were treated similarly and received no irradiation. At time periods corresponding to 0.5, 1.0, 2.0, and 4.0 cycles of the seminiferous epithelium, groups of four sham-irradiated and four irradiated rats were killed and the testes removed for analysis. Net mass of the testes, epididymides, and seminal vesicles; daily sperm production (DSP) per testis and per gram of testis; sperm morphology; and the number of epididymal sperm were determined. There were no statistically significant differences between the sham-irradiated and irradiated groups with respect to any measured variable. In a group of seven surrogate animals of similar body mass, the dose rate of 6.3 mW/g caused a net change in body temperature (via rectal probe) of 1.5 degrees C.

Animals↗
PubMed1983

Further quantification of human spermatogenesis: germ cell loss during postprophase of meiosis and its relationship to daily sperm production.

Potential daily sperm production per gram of testicular parenchyma (PDSP/g) based on pachytene plus diplotene primary spermatocytes was determined by two methods for 10 men aged 26 to 53 years and compared with published daily sperm production per gram parenchyma (DSP/g) based on round spermatid nuclei for these same men. The PDSP/g based on primary spermatocytes was similar (P greater than 0.05) whether determined by histometric analysis (10.0 +/- 1.1 X 10(6] or from homogenates of parenchyma (10.4 +/- 1.0 X 10(6]. When PDSP/g values were compared to DSP/g (5.9 +/- 0.9 X 10(6) for the histometric or 5.5 +/- 0.8 X 10(6) for the homogenate method), 44.9 +/- 6.7% loss of potential sperm production during postprophase of meiosis was detected by the histometric approach and 48.3 +/- 7.9% loss by the homogenate method. Similar results were obtained when testes of 15 additional men aged 26 to 53 years were evaluated by the homogenate method; PDSP/g was 10.6 +/- 0.6 X 10(6), DSP/g was 5.8 +/- 0.5 X 10(6), and the loss during postprophase of meiosis was 45.3 +/- 4.4%. For all 25 men, DSP/g was significantly (P less than 0.01) correlated with PDSP/g (r = + 0.70) and with the percentage loss of potential sperm production during postprophase of meiosis (r = 0.86). Over 73% of the variation in DSP/g could be attributed to variation in the percentage loss during postprophase of meiosis. Whether faulty meiotic divisions and/or degenerating secondary spermatocytes were responsible, almost half of the potential sperm production in these 25 men was lost during postprophase of meiosis.

Adult↗
PubMed1983

Age-related and seasonal variation in the Sertoli cell population, daily sperm production and serum concentrations of follicle-stimulating hormone, luteinizing hormone and testosterone in stallions.

Testes and blood samples were obtained from 201 stallions aged 6 months to 20 years in either December-January (nonbreeding season) or June-July (breeding season) to study the effect of age and season on reproductive parameters. Seasonal differences in the Sertoli cell population of adult (4-20 years old) horses were characterized by a 36% larger number of Sertoli cells in the breeding season than in the nonbreeding season. Seasonal elevation in the Sertoli cell population was associated with an increase in testicular weight and daily sperm production per testis (DSP/testis). Concentrations of luteinizing hormone (LH) and testosterone in serum varied with season. Although follicle-stimulating hormone (FSH) concentrations also tended to be higher in the breeding season, this trend was not statistically significant (P less than 0.08). Sertoli cell numbers averaged over both seasons, like testicular weights, increased with age until 4-5 years of age, but were stabilized thereafter. This age-related difference was also associated with increased concentrations of FSH, LH and testosterone, and with increased DSP/testis. The Sertoli cell population was capable of increasing in the adult horse by fluctuating its size with season. The number of elongated spermatids per Sertoli cell over both seasons increased with age up to 4-5 years of age and was stabilized thereafter. Thus, seasonal and/or age-related differences in DSP/testis were associated with significant elevations in serum concentrations of FSH, LH and testosterone, testicular weights, numbers of elongated spermatids per Sertoli cell and elevation of the Sertoli cell population.

Age Factors↗
PubMed1983

Capillary filtration in the small intestine after irradiation. An experimental study in the cat.

Capillary filtration in the experimentally irradiated small intestine of the cat was studied by measuring the capillary filtration coefficient (CFC). Segments of the small intestine were exposed to X rays of 15, 20, or 25 Gy and studied during the acute gastrointestinal radiation syndrome (4th day) and later (1 and 4 months). On the 4th day CFC had decreased to less than 60% of the original value. Increasing doses resulted in decreasing CFC. One month after irradiation CFC increased, but not to normal levels. After 4 months no further improvement was observed. With the higher doses a secondary decrease in CFC appeared, which might indicate a late effect of irradiation on capillary function.

Animals↗
PubMed1983

Ultrastructural aspects of capillary function in irradiated bowel. An experimental study in the cat.

Irradiated small intestine of the cat has decreased capillary function measured as capillary filtration. This decrease may be due to changes in capillary permeability or decreased capillary area. An electron microscopic study was carried out to examine whether there were any ultrastructural changes consistent with impaired permeability. Cat ileum was irradiated with doses from 10 to 25 Gy and examined 4 days, 1 month, and 4 months after irradiation. In the acute phase (4 days) degenerative endothelial changes were seen and increased with dose. Congestion and microthrombi were also observed. One month after irradiation endothelial changes were still seen after 20 and 25 Gy, and an aggregation of fibrous matter adjacent to the capillary wall was prominent. The endothelial changes were subtle after 4 months, but the pericapillary and stromal fibrosis increased, and an increasing number of collagen fibrils appeared. Micropores disappeared after 20 and 25 Gy but returned later. Pinocytic vesicles were observed after all doses and intervals. The initial decrease in capillary filtration coefficient after irradiation may partly be due to permeability changes caused by endothelial degeneration, whereas the late decrease parallels the increasing pericapillary fibrosis.

Animals↗
PubMed1983

Fanconi's anemia treated by allogeneic marrow transplantation.

Eight patients with Fanconi's anemia were given cyclophosphamide alone (seven patients) or combined with procarbazine and antithymocyte globulin (one patient) followed by marrow grafts from HLA-identical siblings. All patients had engraftment. Seven developed acute and three chronic graft-versus-host disease (GVHD). Three patients died with GVHD and infectious complications (days 19, 56, and 82) and one with an intracerebral hemorrhage (day 540). Four patients are surviving 647-3435 days after grafting, two are well, and two have chronic GVHD that is improving. These results show that Fanconi's anemia can be treated successfully by allogeneic marrow transplantation.

Anemia, Aplastic↗
PubMed1983

Amsacrine in refractory adult acute leukemia: a pilot study of the Southeastern Cancer Study Group.

A phase II pilot study of amsacrine in refractory adult acute leukemia was conducted by the Southeastern Cancer Study Group from May 1979 to August 1980. Amsacrine, 90 mg/m2, was given daily for 5-8 days to 45 patients with acute myeloblastic leukemia, 15 patients with acute lymphoblastic leukemia, and six patients with blastic transformation of chronic granulocytic leukemia. Of the 66 patients entered in the study, 59 (89%) were evaluable for response. Complete remissions were observed in eight of 41 evaluable patients with acute myeloblastic leukemia (20%) and in three of 12 with acute lymphoblastic leukemia (25%). Remissions were short-lived (median, 7.9 weeks; range, 2-27). Toxic effects included the expected myelosuppression (100%), as well as moderate to severe stomatitis (46%), hyperbilirubinemia (30%), and supraventricular tachycardia (1.5%). This cooperative group pilot study confirms previous reports from single institutions that amsacrine is a useful drug in the treatment of refractory adult acute leukemia and is worthy of further study.

Adolescent↗
PubMed1982

Disseminated Mycobacterium avium-intracellulare infection in homosexual men dying of acquired immunodeficiency.

Five homosexual men dying at UCLA Center for the Health Sciences, Los Angeles, with acquired immunodeficiency and Pneumocystis pneumonia, Kaposi's sarcoma, or cryptosporidiosis since May 1981 have all had mycobacteria of the Mycobacterium avium-intracellulare complex cultured from tissues taken just before death or at postmortem examination. Each man had histological evidence of disseminated mycobacterial infection. Acid-fast organisms were seen in macrophages in the lung, spleen, and lymph nodes in all cases and in a variety of additional organs in two cases. Other severe infections were always found at postmortem examination--cytomegalovirus, cryptosporidiosis, and Pneumocystis. Disseminated M avium-intracellulare infection has been so striking in homosexual males dying with acquired immunodeficiency at our institution that we believe a vigorous search for mycobacteria should be made in all such patients. Empiric therapy for mycobacterial infection may be justified in selected cases of immunodeficiency before a specific microbiological diagnosis.

Acquired Immunodeficiency Syndrome↗
PubMed1982

Monitoring the duration of electroconvulsive therapy seizures: 'cuff' and EEG methods compared.

Seizure durations in electroconvulsive therapy (ECT) were determined by both EEG and BP cuff methods in 20 patients receiving 225 seizures. The estimates were highly correlated, with cuff estimates 10% shorter than those by EEG. Routine monitoring of seizure duration by the BP cuff method is recommended, particularly in unilateral ECT. Monitoring seizure time should resolve controversies over the efficacy of different forms of ECT, as well as improve clinical practice where disturbing reports of missed seizures are now documented.

Aged↗