Ultrastructural studies of the hepatocytes after chronic exposure to low levels of halothane.

Adult rats were exposed to 10 ppm or 500 ppm halothane 8 hr/day and 5 days/wk for 8 wk or 4 wk, respectively. In the liver from animals which were exposed to 10 ppm of halothane, the rough endoplasmic reticulum in some hepatocytes accumulated a floccular, electron-dense material which gave the hepatocytes a dense and dark appearance. Increase in the matrical density and C-shaped transformation were observed in the mitochondria of some hepatocytes. In addition to these findings, areas of focal cytoplasmic degradation, dilatation of the bile canaliculi, peribiliary accumulation of lysosomes, and extensive dilatation of the smooth endoplasmic reticulum to form large cytoplasmic vacuoles were also observed in the hepatocytes of animals which had been exposed to 500 ppm halothane. Toxic potential of halothane upon chronic exposure is suggested.     

The development of serum proteins and humoral immunity in opossum `embryos'

The development of serum proteins, immunoglobulins and the immune response was studied in opossum `embryos'. Serum proteins gradually increased from birth to 80 days of age when adult values were obtained. γM immunoglobulins were found at all stages of development but γG immunoglobulins were less regularly present. Those `embryos' which were 5 days or older at the time of immunization had an immune response to bacteriophage f2 and `embryos' 15 days or older responded to a hapten determinant, DNP. γM antibodies were most prominent but γG antibodies could also be detected in the immune response of opossum `embryos'.     

Detection of reticulo-endothelial blockade with low-dose test agent.

Blood clearance and organ extraction of a low-dose reticulo-endothelial test agent, technetium labelled tin colloid (TTC), was measured in groups of rabbits pretreated with reticulo-endothelial blocking agents. Electron microscopy and ultrastructure analysis confirmed that Kupffer cells extracted TTC. Pretreatment with silica caused reduced Kupffer cell uptake and spillover of TTC into the spleen. Pretreatment with sheep red cells caused reduced Kupffer cell uptake and reduced splenic uptake but anti-fibronectin caused only reduced splenic uptake of TTC. TTC is a suitable agent to detect alteration of reticulo-endothelial function.     

Estradiol and insulin: independent effects on eating and body weight in rats.

The effects of ovariectomy and estradiol replacement were determined in streptozotocin-diabetic female rats maintained on daily injections of protamine zinc insulin. Similar changes in food intake and body weight in these animals and in nondiabetic control animals indicate that the effects of estradiol on these measures are probably not dependent on changes in pancreatic insulin secretion. Acute and chronic insulin challenges in ovariectomized rats maintained on estradiol benzoate, nafoxidine or oil were also examined. The effects of insulin were not attenuated by prior estrogen conditioning, and there was no evidence of insulin resistance. These experiments suggest that the effects of estradiol on body weight and food intake in female rats are not dependent upon altered insulin levels nor attenuation of the effects of insulin. Estradiol may exert its influence on eating and body weight via separate and possibly more direct pathways. The data also are consistent with the suggestion that ovariectomy-induced and hypothalamic obesities are separate phenomena.     

Variable frequency trains enhance torque independent of stimulation amplitude

AIM: Variable frequency trains have been reported to enhance force of fatigued human skeletal muscle. More rapid calcium turnover and/or enhanced stiffness may be responsible for the augmented torque-time integral during surface stimulation at moderate amplitude. In contrast, it has recently been suggested that variable frequency train enhancement occurs only at low forces as a result of preferential stimulation of fast fibres and/or altered motor unit recruitment. If correct, this would limit the practical benefit of variable frequency trains. Accordingly, we tested the hypothesis that torque augmentation by variable frequency trains in fatigued skeletal muscle was independent of stimulation amplitude. METHODS: The m. quadriceps femoris of six males was stimulated with constant frequency trains (six 200-micros square waves separated by 70 ms) or variable frequency trains (first interpulse interval 5 ms) at an amplitude that initially evoked approximately 25 or approximately 50% of maximal voluntary isometric torque. RESULTS: After 180 constant frequency trains (50% duty cycle), isometric peak torque decreased approximately 63%. In fatigued muscle, variable frequency trains enhanced the torque-time integral by approximately 23% over that for constant frequency trains and this effect was independent of stimulation amplitude. This was due to greater peak torque and less slowing of rise time. CONCLUSION: These responses show that the torque-time integral can be enhanced at both moderate and high stimulation amplitudes. As such, it is suggested that neither recruitment nor preferential activation of fast muscle is responsible for the "catch-like" property that can be demonstrated in fatigued human skeletal muscle.     

Predictors of HIV Risk Among College Students: A CHAID Analysis1

SUMMARY The purpose of this study was to identify predictors of risk behaviors among college students and to determine how students differed in HIV risk practices. Participants were from six colleges and universities in a large southeastern metropolitan area. The present analysis was limited to participants who were 18 to 25 years of age; single; White, African American, or Asian; and reported initiation of sexual intercourse. The results demonstratedsignificant associations of gender and race with having sex within the past3 months, number of partners, condom use, length of time one knew one's sexual partner, substance use, and asking one's partner about sexualhistory. Using Chi-Square Automatic Interaction Detection (CHAID), the strongest predictor of condom use was noted to be gender, and the strongest predictor of number of partners was race. The findings of this study indicate that HIV risk factors vary dependingon a college student's ethnicity, gender, academic status, and substanceuse. Most importantly, African American men, particularly men who use drugs, and White and Asian men who use alcohol tend to report higher numbers of sexual partners. Females, particularly upperclass White females, and White men who do not use alcohol report infrequent condom use. These findings areuseful for health educators who have begun to recognize the importance ofconsidering the HIV risk factors of students and incorporating informationrelated to these factors into HIV prevention programs. From the results ofthis study, we have several suggestions that health educators and researchersmay want to consider when developing programs for college students: 1. Although students may not need extensive information about basic HIVfacts, they may need reinforcement of the information. In particular, students need to be made aware that lambskin condoms do not offer protection against HIV transmission. 2. Females need to be encouraged and taught the skills to negotiate theuse of and to actually use condoms. These skills need to be reinforced throughout college, particularly as women adopt other methods of birth control (i.e., the pill). 3. The general acceptance of condom use among African Americans and Asians may be a useful tool for the health educator. Promoting and reinforcingthis norm and behavior, while addressing some of the other risk factors inthese groups, may be a particularly effective approach to HIV prevention. 4. For White students whose condom use rates are lower, messages can include the use of condoms for STD and pregnancy protection. Messages for male students could include control over preventing pregnancy or sharing control for pregnancy prevention. 5. Couples often abandon using condoms when they feel they know each other “well enough.” Some guidelines for when to give up condoms might also be given to provide couples with responsible and realistic directions for minimizing their risk when choosing to engage in unprotected sex. These guidelines would include HIV testing two times at least 6 months apart, no evidence of STDs in either partner, and a commitment of both partners to a monogamous relationship. 6. When addressing the number of sexual partners as a risk factor, African American men and women may hold the greatest potential for change, given the greater likelihood of multiple partners in these groups. 7. With respect to drug and alcohol use, health educators may want to include discussions about the influence of drugs (particularly for African American students) and alcohol (particularly for White and Asian students) on inhibiting logical decision-making as it relates to sexual intercourse.     

Nonhereditary p53 mutations in T-cell acute lymphoblastic leukemia are associated with the relapse phase

We have previously reported that greater than 60% of human leukemic T- cell lines possess mutations in the p53 tumor suppressor gene. To determine whether T-cell acute lymphoblastic leukemia (T-ALL) patient samples possess p53 mutations, we screened peripheral blood-and bone marrow-derived leukemia samples, taken at diagnosis and at relapse, for p53 mutations. Exons 4 through 9 and selected intron regions of the p53 gene were analyzed using polymerase chain reaction-single-strand conformation polymorphism and direct sequencing. p53 mutations were found in 0 of 15 T-ALL diagnosis samples, as compared with 10 of 36 (28%) T-ALL relapse samples. To determine whether p53 mutations play a role in the recurrence (relapse) of T-ALL, two special groups of T-ALL patients were studied: (1) a group of 8 relapse patients whose disease was refractory to chemotherapeutic treatment, and (2) a group of 6 "paired" T-ALL cell samples from patients for whom we possess both diagnosis and relapse samples. Three of 8 relapsed patients (37.5%) whose disease was refractory to the reinduction of remission by chemotherapy possessed missense mutations of the p53 gene. All 3 cases had mutations in exon 5. Among the paired samples, 3 of 6 patients harbored p53 mutations at disease recurrence, but possessed only wild- type p53 alleles at diagnosis. One case had mutation on exon 4, 1 case in exon 5, and 1 case in exon 8 with loss of heterozygosity. These data clearly indicate that recurrence of T-ALL is associated with missense mutations in p53. Our results indicate that (1) mutations of p53 do occur in T-ALL in vivo, and such mutations are associated with the relapse phase of the disease; and (2) p53 mutation is involved in the progression of T-ALL. This conclusion is supported by our observation that the introduction of T-ALL-derived mutant p53 expression constructs into T-ALL cell lines further increases their growth rate in culture, enhances cell cloning in methylcellulose, and increases tumor formation in nude mice.     

碱离子水饮用后血小板聚集率的的变化(附30例报告)

目的:报告30例饮用豪斯牌碱离子水前、后血小板聚集率的变化。方法:饮用碱离子水前、后(2～3月,>3～6月)作比浊法血小板聚集试验,以1分钟、5分钟及5分钟内最大聚集率(Max％)为指标,同时检测部分血粘度指标及凝血因子,并用自动生化仪检测血糖、血脂、主要电解质及部分肝、肾功能。结果:饮碱离子水后,血小板聚集率明显下降,而以疾病组(Max>80％)下降尤为明显,P均<0.001。饮碱离子水后血小板聚集率的下降,部分可能与损伤的血管内皮得到修复有关。主要电解质及部分肝、肾功能无明显异常改变。结论:由于心、脑血管血栓性疾病患者血小板聚集率多明显升高,饮碱离子水后血小板聚集率明显下降,且长期饮用对主要电解质及部分肝、肾功能无明显异常改变,作者认为碱离子水使用方例、安全、有效、价廉,因而对心、脑血管血栓性疾病防治方面可能是一种积极的辅助方法,值得临床进一步探索。