Dichotomous effects on lymphatic transport with loss of caveolae in mice

AIM

Fluid and macromolecule transport from the interstitium into and through lymphatic vessels is necessary for tissue homeostasis. While lymphatic capillary structure suggests that passive, paracellular transport would be the predominant route of macromolecule entry, active caveolae-mediated transcellular transport has been identified in lymphatic endothelial cells (LECs) in vitro. Caveolae also mediate a wide array of endothelial cell processes, including nitric oxide regulation. Thus, how does the lack of caveolae impact "lymphatic function"?

METHODS

Various aspects of lymphatic transport were measured in mice constitutively lacking caveolin-1 ("CavKO"), the protein required for caveolae formation in endothelial cells, and in mice with a LEC-specific Cav1 gene deletion (Lyve1-Cre x Cav1^flox/flox ; "LyCav") and ex vivo in their vessels and cells.

RESULTS

In each model, lymphatic architecture was largely unchanged. The lymphatic conductance, or initial tissue uptake, was significantly higher in both CavKO mice and LyCav mice by quantitative microlymphangiography and the permeability to 70 kDa dextran was significantly increased in monolayers of LECs isolated from CavKO mice. Conversely, transport within the lymphatic system to the sentinel node was significantly reduced in anaesthetized CavKO and LyCav mice. Isolated, cannulated collecting vessel studies identified significantly reduced phasic contractility when lymphatic endothelium lacks caveolae. Inhibition of nitric oxide synthase was able to partially restore ex vivo vessel contractility.

CONCLUSION

Macromolecule transport across lymphatics is increased with loss of caveolae, yet phasic contractility reduced, resulting in reduced overall lymphatic transport function. These studies identify lymphatic caveolar biology as a key regulator of active lymphatic transport functions.

Laparoscopic-assisted removal of gastric trichobezoar; a novel technique to reduce operative complications and time

Trichobezoar complicates trichophagia. It can provide a diagnostic challenge due to the variety of presenting features. Surgical removal is usually required for relief of symptoms and prevention of further complications. We describe 2 cases of gastric trichobezoar, and present a novel laparoscopic-assisted technique of removal of large trichobezoars involving the use of an Alexis wound retractor. This is advantageous as it keeps peritoneal cavity and skin clean and the gastric wound is protected from trauma by repeated instrumentation. Excellent access to the stomach is provided. A larger foramen means the bezoar could be removed quicker than through a port, reducing operative time.

Validation of an independent living scale for post-acute rehabilitation applications

The Independent Living Scale (ILS) was developed in a post-acute traumatic brain injury (TBI) rehabilitation facility over a 15-year period to assess three main areas: (1) activities of daily living, (2) behaviour, and (3) initiation. The purpose of this study was to examine the psychometric properties of the ILS, including test--retest stability, construct validity, and statistical fit. Statistical analysis was completed on all weekly scores between the years 1986-1995 (n = 5250). A previous study showed ILS inter-rater reliability to be 0.85 and convergent validity 0.82--0.87. This study demonstrated a test--retest stability of 0.72, the Kaiser-Meyer-Olkin Measure of Sampling Adequacy 0.94 (marvelous), and a Bartlett Test of Sphericity result of 'scale items independent'. The ILS was shown to have good construct validity, inter-rater reliability, internal consistency, instrument stability, and convergent validity.

Women's self-perception and self-care practice: implications for health care delivery

Mexican American women experience unique health care needs related to integration of Mexican and American cultures. To learn how to better promote self-care practices and service utilization in women of Mexican origin living in Texas, researchers used a qualitative approach to interview a convenience sample of 11 low-income women attending a health clinic. Researchers collected narrative data about the women's perceptions of health, wellness, and self-care. Using the matrix approach described by Miles and Huberman, we organized findings around women's roles, including participants' descriptions of themselves, their health and wellness awareness, self-care practices for health/illness and wellness/nonwellness, barriers to self-care, origin of self-care practices, and perceptions of life control. Implications for health planning and service delivery are presented.

The effect of video-based interventions on self-care

Caregivers for dependent, elderly community dwellers are frequently themselves at risk for illnesses exacerbated by stress. This study evaluates a videotape scenario intervention designed to increase self-care behaviors in three groups of caregivers randomly assigned to a control or to one of two experimental groups. Within the 6- to 8-week trial, attitudes toward self-care became more positive in the experimental groups, and all groups reported endorsement of behavioral changes related to self-care.

Postponing sexual intercourse among urban junior high school students-a randomized controlled evaluation

PURPOSE

To describe a randomized, controlled evaluation of a school-based intervention to delay sexual intercourse among urban junior high school students.

METHODS

Six Washington, D.C., junior high schools were randomly assigned to the intervention or nonintervention control condition for an educational program. During the first school year, seventh graders (n = 582) from the six schools obtained written parental consent to participate. Three health professionals (one per intervention school) implemented the program, which consisted of reproductive health classes, the Postponing Sexual Involvement Curriculum, health risk screening, and "booster" educational activities during the following (eighth grade) school year. Cross-sectional surveys were administered at baseline, the end of the seventh grade, and the beginning and end of the eighth grade. Intervention and control group differences in virginity, attitudes toward delayed sex and childbearing, and sexual knowledge and behavior were assessed at all four time points.

RESULTS

At baseline, 44% of the seventh grade males and 81% of the seventh grade females reported being virgins. At the end of the seventh grade (first follow-up), after controlling for baseline study group differences, intervention-group females were more likely to report virginity, self-efficacy to refuse sex with a boyfriend, and the intention to avoid sexual involvement during the following 6 months. At the end of the eighth grade, significantly more intervention- than control-group females reported virginity, birth control use at last intercourse (for nonvirgins), and knowledge of adolescent reproductive health and confidentiality rights. No changes in virginity, self-efficacy to refuse sex, or sexual intent for the next 6 months were observed among male participants at any time during the study. However, on all three follow-up surveys, intervention-group males scored significantly higher than their control-group counterparts in knowledge of birth control method efficacy. No change in attitudes toward abstinence was observed for either gender at any follow-up point.

CONCLUSIONS

Gender differences in baseline sexual activity rates and in various study outcomes suggest a possible need for separate, gender-specific intervention activities that can adequately address the social and cognitive needs of both sexes.

Parenteral vs oral antibiotics in the prevention of serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia: a meta-analysis

OBJECTIVE

To determine whether parenteral antibiotics are superior to oral antibiotics in preventing serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia.

METHODS

Using the MEDLINE database, the English language literature was searched for all publications concerning bacteremia, fever, or Streptococcus pneumoniae from 1966 to January 1, 1997. All nonduplicative studies with a series of children with S. pneumoniae occult bacteremia having both orally treated and parenterally treated groups were reviewed. Children were excluded from individual studies if at the time of their initial evaluation they were immunocompromised, had a serious bacterial infection, underwent a lumbar puncture, or did not receive antibiotics.

RESULTS

Only 4 studies met study criteria. From these studies, 511 total cases of S. pneumoniae occult bacteremia were identified. Ten of 290 (3.4%) in the oral group and 5 of 221 (2.3%) in the parenteral antibiotic group developed serious bacterial infections (pooled p-value = 0.467, pooled OR = 1.48; 95% CI, 0.5-4.3). Two patients in the oral group (0.7%) and 2 patients in the parenteral group (0.9%) developed meningitis (pooled p-value = 0.699, pooled OR = 0.67; 95% CI, 0.1-5.1).

CONCLUSION

The rates of serious bacterial infections and meningitis did not differ between children who were treated with oral and parenteral antibiotics. The extremely low rate of complications observed in both groups suggests no clinically significant difference between therapies. A study with >7,500 bacteremic children (or >300,000 febrile children) would be needed to have 80% power to prove parenteral antibiotics are superior to oral antibiotics in preventing serious bacterial infections.

Automatic tumor segmentation using knowledge-based techniques

A system that automatically segments and labels glioblastoma-multiforme tumors in magnetic resonance images (MRI's) of the human brain is presented. The MRI's consist of T1-weighted, proton density, and T2-weighted feature images and are processed by a system which integrates knowledge-based (KB) techniques with multispectral analysis. Initial segmentation is performed by an unsupervised clustering algorithm. The segmented image, along with cluster centers for each class are provided to a rule-based expert system which extracts the intracranial region. Multispectral histogram analysis separates suspected tumor from the rest of the intracranial region, with region analysis used in performing the final tumor labeling. This system has been trained on three volume data sets and tested on thirteen unseen volume data sets acquired from a single MRI system. The KB tumor segmentation was compared with supervised, radiologist-labeled "ground truth" tumor volumes and supervised k-nearest neighbors tumor segmentations. The results of this system generally correspond well to ground truth, both on a per slice basis and more importantly in tracking total tumor volume during treatment over time.

A causal functional explanation of maintaining a dependent elder in the community

A causal functional structure demonstrates how a perpetual process, like caregiving, maintains itself. The caregiver functional learning model was used to identify factors influencing caregivers when maintaining dependent elders in the community. These factors include seriousness of illness, power, burden, care quality, self-assurance, an understanding of the elder's needs, and time spent in caregiving. This five-stage theoretical model was tested using a sample of 70 caregivers. Findings supported two of the theoretical relationships: seriousness of illness (beta = .60) with burden (R2 = 0.35), and self-assurance (beta = .36) with time (R2 = 0.18). Three new relationships were added with the empirical model: power (beta = .48) with burden (R2 = 0.52), seriousness of illness (beta = .36) with self-assurance (R2 = 0.11), and burden (beta = .33) with time (R2 = 0.24). A causal functional structure can be used to explain how the phenomenon of caregiving maintains itself.

Perfluorocarbons: future clinical possibilities

Perfluorocarbons are now being used as oxygen carriers in clinical settings. Because these chemicals may have a role as a blood substitute, in organ preservation, and in the management of respiratory failure, we have reviewed some of the research leading to these applications.

Medical image analysis with fuzzy models

This paper updates several recent surveys on the use of fuzzy models for segmentation and edge detection in medical image data. Our survey is divided into methods based on supervised and unsupervised learning (that is, on whether there are or are not labelled data available for supervising the computations), and is organized first and foremost by groups (that we know of!) that are active in this area. Our review is aimed more towards 'who is doing it' rather than 'how good it is'. This is partially dictated by the fact that direct comparisons of supervised and unsupervised methods is somewhat akin to comparing apples and oranges. There is a further subdivision into methods for two- and three-dimensional data and/or problems. We do not cover methods based on neural-like networks or fuzzy reasoning systems. These topics are covered in a recently published companion survey by keller et al.

Long-term follow-up of post-acute traumatic brain injury rehabilitation: a statistical analysis to test for stability and predictability of outcome

A high percentage of the estimated 500,000 traumatic brain injuries (TBI) in the US every year occur with young people who will face many years of neurobehavioral and economic consequences. This study examined the long-term stability of outcome after post-acute TBI rehabilitation and possible predictors of long-term outcome based on a 127-item survey of 332 clients up to 14 years post-discharge. Correlational, factor, and multiple regression analysis indicated positive long-term outcome stability following rehabilitation with the exception of vocational status, which decreased over the same time period. A number of possible explanations for this occupational anomaly are suggested. Rating scale scores and latency-to-rehabilitation proved to be better predictors of long-term outcome than demographic data.

Do oral antibiotics prevent meningitis and serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia? A meta-analysis

OBJECTIVE

To determine whether oral antibiotics prevent meningitis and serious bacterial infections in children with Streptococcus pneumoniae occult bacteremia.

DATA SOURCES

Using the Medline database, the English-language literature was searched for all publications concerning bacteremia, fever, or S pneumoniae from 1966 to April 1996.

STUDY SELECTION

All studies that included a series of children with S pneumoniae occult bacteremia containing orally treated and untreated groups. Children were excluded from individual studies if they were immunocompromised, had a serious bacterial infection, underwent a lumbar puncture, or received parenteral antibiotics.

DATA EXTRACTION

Three authors independently reviewed each article to determine the number of eligible children and the outcome of children meeting entry criteria.

DATA SYNTHESIS

Eleven of 21 studies were excluded, leaving 10 evaluable studies with 656 total cases of S pneumoniae occult bacteremia identified. Patients who received oral antibiotics had fewer serious bacterial infections than untreated patients (3.3% vs 9.7%; pooled odds ratio, 0.35; 95% confidence interval, 0.17 to 0.73). Meningitis developed in 3 (0.8%) of 399 children in the oral antibiotic group and 7 (2.7%) of 257 untreated children (pooled odds ratio, 0.51; 95% confidence interval, 0.12 to 2.09).

CONCLUSION

Although oral antibiotics modestly decreased the risk of serious bacterial infections in children with S pneumoniae occult bacteremia, there was insufficient evidence to conclude that oral antibiotics prevent meningitis. Published recommendations that oral antibiotics be administered to prevent serious bacterial infections in children with possible S pneumoniae occult bacteremia should be reevaluated in light of the lower risk of sequelae from S pneumoniae occult bacteremia and newer data concerning side effects from treatment.

The caregiving story: how the narrative approach informs caregiving burden

The burdens of giving care to a chronically ill or dependent family member can be overwhelming. The therapeutic utilization of narrative can assist elderly female caregivers to transform their feelings of depression and burden into a healthy acceptance of the required care and disabilities of the elder for whom they care. This technique, which assists clients to restory negative aspects of their perceived reality, has emerged from the theoretical framework of postmodernism. Using the narrative approach to a family case study involving a daughter and dependent mother, this article examines interventions that can facilitate the positive development of a client's caregiving story.

Activation of cytokine production and adhesion molecule expression on THP-1 myelomonocytic cells by macrophage colony-stimulating factor in combination with interferon-gamma

THP-1 myelomonocytic leukemia cells cultured with either macrophage colony-stimulating factor (M-CSF) or interferon-gamma (IFN-gamma) alone produce, at best, only low levels of interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha). However, combinations of the two factors resulted in at least 3- to 20-fold greater amounts of IL-1 beta and TNF-alpha than would have been predicted by additive mechanisms. This enhanced cytokine production was observed when M-CSF and IFN-gamma were added simultaneously or when M-CSF was added 24 h after addition of IFN-gamma to the cells. Similar results were obtained with fresh human peripheral blood cells treated with IFN-gamma + M-CSF. Cycloheximide treatment of the cultures containing M-CSF and IFN-gamma inhibited the production of IL-1 beta and TNF-alpha. Northern blotting studies revealed no effect of IFN-gamma alone on IL-1 beta or TNF-alpha mRNA production. IL-1 beta and TNF-alpha mRNA expression was observed at 2 and 6 h after treatment with M-CSF or IFN-gamma + M-CSF. Higher TNF-alpha mRNA expression was observed at 2 and 6 h after treatment with IFN-gamma + M-CSF, and higher IL-1 beta mRNA expression was observed at 2 h after treatment with IFN-gamma + M-CSF compared with mRNA levels observed for cells cultured only with M-CSF. These results suggest that the augmented cytokine production resulting from treatments with combinations of M-CSF and IFN-gamma occurs due to increased cytokine mRNA and increased cytokine protein synthesis. In addition to up-regulating cytokines, combinations of IFN-gamma and M-CSF resulted in augmented cell surface expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. This was accompanied by morphological and functional changes that included plastic adherence, extensive homotypic aggregation, and a macrophage-like appearance. These phenotypic changes and enhancements in cytokine expression and cell surface molecule expression may be related to activation of monocytic cells to become cytotoxic effectors by M-CSF and IFN-gamma combinations. In vitro cytotoxicity against A-375 melanoma cells was greatest for cultures that contained M-CSF and IFN-gamma in combination.

Enhancing critical-thinking skills: faculty-student partnerships in community health nursing

The enhancement of critical-thinking skills empowers students to participate in the building of healthy environments in a variety of settings. The authors describe the development and implementation of unique classroom strategies emphasizing the use of critical thinking by students, the forging of faculty-student partnerships in community health nursing, and the potential impact of these strategies on the expanding horizons of practice.

Rehabilitation technology assessment practices in vocational rehabilitation agencies

A rehabilitation technology assessment is an essential element in the array of rehabilitation technology services provided for vocational rehabilitation (VR) clients. As a part of a comprehensive survey of rehabilitation technology services in VR agencies, information was collected on current practices in rehabilitation technology assessment. Some variation in length, components included, and professionals involved were found among agencies. A complete description of these assessments as reported by VR agencies is discussed and commonalities in current practice are described.

Levamisole causes differential cytokine expression by elicited mouse peritoneal macrophages

Thioglycolate-elicited peritoneal macrophages from normal C57B1/6J mice were examined in vitro for bacterial lipopolysaccharide (LPS)-stimulated interleukin-1 (IL-1), IL-6, and tumor necrosis factor (TNF) production. Macrophages from mice administered a single oral dose of levamisole (3 mg/kg) 1 to 4 days prior to macrophage harvest demonstrated a twofold enhancement of IL-1 production compared to vehicle-treated mice. In contrast, IL-6 production and TNF production by the same macrophages were inhibited up to 36 and 62%, respectively, compared to production by macrophages harvested from vehicle-treated mice. Similar results were observed when IL-1 production and TNF production were followed in peritoneal exidate cells directly stimulated with levamisole in vitro. The ex vivo LPS-stimulated IL-1 production was enhanced 4 days after macrophage elicitation, whereas TNF and IL-6 production returned to baseline by 72 h after macrophage recruitment and augmentation. No evidence could be found for the presence of inhibitors of TNF or IL-6. The specificity of the IL-1, IL-6, and TNF bioactivities was demonstrated by neutralization with specific antisera. Immunoprecipitation studies of supernatants from biosynthetically labeled macrophages also revealed augmented IL-1 production and decreased IL-6 and TNF, indicating that levamisole may have affected cytokine production at the translational level. Kinetics studies revealed that ex vivo release of IL-6 and TNF by macrophages from levamisole-dosed mice was delayed compared to production of these cytokines by macrophages harvested from mice given vehicle only. The results may explain, in part, the reported ability of levamisole to ameliorate cases of rheumatoid arthritis or other autoimmune and inflammatory diseases by affecting the relative levels of cytokines produced by macrophages recruited to sites of injury, which are associated with inflammation and acute-phase protein synthesis.

Older adults and daily living task profiles

This paper describes data generated from a comprehensive study in which human factors techniques were applied to the analysis of 25 personal and instrumental activities of daily living (ADLs) performed by 60 older adults (age 55 to 93 years) living in the community. Demand profiles generated from task analysis of video-taped ADLs identify the demands inherent in task activities and the objects and environments associated with them. Examples of four different approaches to examine ADL performance using demand profiles are presented: global descriptions of demands across all ADL tasks, task component profiles, task-specific profiles, and action profiles.

In what ways, if any, are child abusers different from other parents?

In recent years a variety of alternative theoretical models have been developed to aid our understanding and to guide research in this area. This essay considers in particular the psychiatric model and the social interactional model of child abuse, together with research studies comparing physically abusive and non-abusive families. It will be concluded that research has pinpointed several important distinguishing features in the behaviour of abusive versus non-abusive families. A pattern of behaviour with their child is displayed by abusers that is proportionately more aversive than for non-abusers, and observations of parent-child interactions have revealed qualitative differences in patterns of interaction which seem to be a significant factor in the differentiation of abusive from non-abusive families.

Interstitial deletion (6) (q11----q15) in an infant with congenital abnormalities

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Social support, perceived control, and well-being: a study of an environmentally stressed population

Interviews were conducted with elderly residents of an area targeted for massive redevelopment. Social support was considered simultaneously with health and personal control beliefs in relation to well-being, and the unresolved issue of the sufficiency of one support figure was explored. Health, control, and support each emerged as independent predictors of after and life satisfaction, and affect was significantly lower for those with no close support figure than for those with one close relationship. The results suggest that one close support figure may be sufficient to promote well-being, but alternative interpretations are possible.

Characterization of a plasmid in isolates of Corynebacterium sepedonicum

Lysis of mid-log phase cells of the Gram-positive bacterium, Corynebacterium sepedonicum, by a combination of lysozyme treatment and incubation with alkaline sodium dodecyl sulfate at 56 degrees C led to the recovery of a single plasmid. The plasmid was purified in CsCl density gradients, and its molecular weight estimated to be 31 megadaltons (46 kilobases), as determined from its relative mobility in agarose gels, from its contour dimensions in electron micrographs, and from the size of the fragments generated when it was cleaved with various restriction endonucleases. Thirteen widely divergent isolates of C. sepedonicum were screened for the presence of plasmid, and of these, 11 were shown to harbour a single plasmid at a level of about 30 copies per cell. Cleavage of the plasmid with PstI gave an identical banding pattern in agarose gels for the fragments from all of the plasmid-carrying isolates. The relevance of plasmid incidence and distribution in C. sepedonicum is discussed in relation to the possibility of developing a test for the detection of bacterial ring rot by using plasmid DNA as a hybridization probe.

Social support and well-being: preliminary indicators based on two samples of the elderly

The structure of social support and its relation to health, affect, and life satisfaction are compared for two samples of the elderly. The first is a national representative sample; the second is a distressed sample from South Miami Beach. Although there are similarities in the structure of social support across the two groups, those in the Miami Beach sample report fewer support figures, and far fewer within geographic proximity, than do those in the national sample. This comparative network impoverishment is particularly marked for male respondents and is accentuated by a high number of isolates in this group. In addition, stronger relationships are found between support network size and affect, and among affect, life satisfaction, and health in the South Miami Beach sample. Older men in poor health and without supportive relationships are targeted as a particularly high risk subgroup. The discussion includes a focus on personal, situational, and life span differences related to variations in support and well-being and a consideration of implications for more recent waves of elderly sun-belt migrants.

Comparison of the echocardiographic and hemodynamic diagnosis of rheumatic tricuspid stenosis

Two-dimensional echocardiography has proved to be reliable in the diagnosis of mitral, aortic and pulmonary stenosis. Its role in the diagnosis of rheumatic tricuspid stenosis is still being defined; therefore, the tricuspid valve echograms of 147 patients with rheumatic heart disease were examined. Thirty-eight of these patients also underwent hemodynamic evaluation. Tricuspid stenosis was defined echocardiographically as diastolic anterior leaflet doming, thickening and restricted excursion of the other two tricuspid leaflets and decreased separation of the leaflet tips. Using these criteria, the sensitivity and specificity of the echocardiogram in detecting tricuspid stenosis were 69 and 96%, respectively, in the group of 38 patients who had both echocardiographic and hemodynamic evaluations. However, when the smaller group of 17 patients who had simultaneous right atrial and right ventricular pressure recordings were considered separately, there was complete agreement between the echocardiographic and hemodynamic data. Thus, the two-dimensional echocardiogram is a sensitive and specific test for diagnosing rheumatic tricuspid stenosis. In addition, these data provided an opportunity to determine the prevalence of tricuspid stenosis in this group of patients with chronic rheumatic valvular disease. Tricuspid stenosis was present in 14 (9.5%) of the total group of 147 patients who had two-dimensional echocardiograms, and in 10 (26.3%) of the 38 who had both echocardiographic and hemodynamic studies. In patients with rheumatic heart disease about to undergo cardiac catheterization, an echocardiographic study should prove useful in making the diagnosis of tricuspid stenosis.

Permeability pulmonary edema caused by venous air embolism

A 22-yr-old man developed severe pulmonary edema after blowing air into tubing connected to a catheter inserted in a vein in his forearm. Pulmonary edema was rapid in onset, peaking in intensity about 12 h after the air had been insufflated. The patient's edema fluid to plasma protein concentration ratio of 0.79 showed that the edema fluid was rich in protein. Vascular pressures were normal except for mild pulmonary arterial hypertension and systemic hypotension. The patient's clinical course, edema fluid protein concentration, and vascular pressures were characteristic of an increased microvascular permeability type of pulmonary edema. The patient recovered fully within 48 h of the air infusion. His response to venous air embolism was similar to findings in an experimental model of pulmonary edema in sheep infused with venous air emboli. As long as air is not infused continuously for long periods or in very large amounts, this disorder is probably self-limiting, and supportive care may be the only treatment necessary.

Thin-foil fabrication

A method has been developed to produce seamless, freestanding plastic cylinders with dimensions up to 18 cm in diameter, 4 cm in height and with mass density from 15 mug/cm to 300 mug/cm (approximately 0.15 to 3 mu thick). The polyvinyl formal resin may be subsequently coated with a variety of material by vapor deposition. The method employs standard thin-foil fabrication techniques modified for use in cylindrical geometry and results in uniform reproducible cylinders.

Purine metabolism and differential inhibition of spore germination in Phytophthora infestans

An analysis of the effect of various purines and pyrimidines on the germination process in three different isolates of the late blight fungus, Phytophthora infestans, revealed increased rates of indirect germination in one isolate by adenine, hypoxanthine, and the riboside of dimethylaminopurine. This observation coupled with the capacity of sporangia of the race affected (1.2.3.4) for the uptake and interconversion of purines, as demonstrated by experiments with labelled purines under in vivo and in vitro conditions, pointed to hypoxanthine as a key intermediate in the purine metabolism directly associated with spore formation and development. This enhanced germination contrasted sharply with the almost complete arrest of indirect germination that occurred when sporangia were incubated with the purine analogue, benzimidazole, or with either of the respiratory inhibitors, sodium azide and 2,4-dinitrophenol. The pattern of differential inhibition exhibited by sporangia versus zoospores upon treatment with actinomycin D, 4-FLUOROURACIL, OR CYCLOHEXIMIDE INDICATED THat continued translation on preformed messenger RNA may be one essential requirement for the formation and release of zoospores, whereas their subsequent germination and development may depend upon renewed transcription as well.

Composition of DNA from Phytophthora infestans

Deoxyribonucleic acid was extracted from the late blight fungus, Phytophthora infestans, and partially characterized in terms of its physical and chemical properties. Hydrolysis of the purified DNA followed by electrophoretic analysis failed to demonstrate the presence of constituents other than those characteristically found in DNA. Analysis of the nucleotide composition based on thermal denaturation studies yielded values for the percentage guanine–cytosine which are consistent with those reported for other members of the Phycomycetes.