Short-Term In Vitro Culture and Molecular Analysis of the Microsporidian, Enterocytozoon bieneusi

ABSTRACT. The microsporidium, Enterocytozoon bieneusi , causes a severe, debilitating, chronic diarrhea in patients with the acquired immunodeficiency syndrome. Specific diagnosis of intestinal microsporidiosis, especially due to Enterocytozoon , is difficult and there is no known therapy that can completely eradicate this parasite. Preliminary studies indicate that a short term (about 6 months) in vitro culture of this parasite yielding low numbers of spores, may be established by inoculating human lung fibroblasts and/or monkey kidney cell cultures with duodenal aspirates and or biopsy from infected patients. The cultures may subsequently be used for the isolation and molecular analysis of parasite DNA.     

Trade-offs in Energy Allocation During Lactation

SYNOPSIS. During lactation, mothers require energy to meet bothmaternal and offspring requirements. If a mother exports toomuch energy to dependent offspring (in milk), her weight lossmay be excessive and maternal risk may increase. Conversely,too little energy allocation to offspring may reduce the growthrate or induce mortality of dependent offspring. This paradigmwas evaluated in cotton rats (Sigmodon hispidus) supportingsmall (3 pup) and large (6 pup) litters from early to late lactation.Several types of evidence indicate that physiological constraintslimit the ability of mothers with large litters to provide resourcesto offspring. Mothers with large litters produced a dilute,energy-poor milk and their rates of food intake, weight lossand energy export per litter appeared to approach physiologicalmaxima. Whereas the energy exported to pups in small littersincreased from early to late lactation, the energy flow perpup in large litters was consistently low; consequently, offspringin large litters had low growth rates. An increase in eithermaternal food intake or weight loss (catabolism of maternaltissue) could have provided additional energy to offset thelow growth rate of pups in large litters. However, mothers withlarge litters did not substantially increase their food intakeor weight loss compared with mothers supporting small litters.These results indicate that the maternal support of offspringin large litters is limited. The pattern of energy allocationshown by cotton rats with large litters likely reflects a compromisebetween meeting maternal and offspring energy requirements (cf.,Parker and Macnair, 1979). The energy flow is greater than optimalfor the parent but less than optimal for the offspring. Lessmaternal-offspring conflict occurs in small than large littersbecause offspring in small litters maintain a high growth rateat a relatively low maternal cost. Yet, under favorable environmentalconditions, the reduction in maternal-offspring conflict hasno apparent fitness benefit.     

Changes in the Architecture of Cancellous Bone in the Femora of Developing Mice as a Result of Short Duration Hypergravity

SYNOPSIS. Mice were used as a model system to demonstrate theeffects of increased loading on the trabecular bone in the developingproximal femur. A two-dimensional free body diagram revealedthat because the femur is normally held in a horizontal positionduring support, functional loading resulted in a net posteriorbending moment and a muscle generated axial compressive loadthat was 7.7 times the normal support weight for that limb.Experimental treatment consisted of four times normal gravityfor 10 min, six times per day for 30 days in addition to unrestrainednormal exercise. Unrestrained normal exercise served as thecontrol. An animal whose foot was amputated by his mother shortlyafter birth was used as a less than normal load example forcomparison with the hypergravity and control groups. All groupswere treated for 30 days. Two areas of trabecular bone wereexamined: a proximal central webbing area that may be underpredominantly tensile loading much of the time, and a more distalarea near the third trochanter that presumably experiences bendingstresses when the animal is exposed to normal activity or hypergravity.Results indicate that: 1) The central webbing area appears tohave a similar mass of bone regardless of loading conditions;however, with increased loading the trabeculae become orientedin directions that approximate directions of presumed principaltensile stresses. 2) There is no genetically predetermined amountof bony tissue in the third trochanter area; when the limb isrelatively unloaded no trabeculae are present, as the loadingincreases trabecular bone is formed. In the hypergravity group,trabeculae in the area of the third trochanter increased inlength and complexity and became more centrally positioned inthe lumen of the femur, a position that presumably would allowthe femur to better resist bending moments. These results demonstratethat short duration, high intensity functional loading can stimulategrowth of trabecular bone, and further, specific types of functionalloading can be correlated with specific architectural changes.     

Differential Rates of Uptake of Glucose, Fructose and Sucrose by Pea Stem Protoplasts

Protoplasts from growing regions of etiolated pea stems takeup glucose more rapidly than fructose when supplied for briefperiods at low concentrations. The uptake of the two hexosesis differentially inhibited by galactoac and by reagents thatcurtail ATP synthesis, and uptake of one hexose is not preventedby the other, even at a 100-fold excess. Sucrose uptake is muchslower than that of either hexose and is correlated with theappearance of invertase activity in the medium. Label from [¹⁴C-glc]-sucroseis taken up more rapidly than from [¹⁴C-fru]-sucrose. It isconcluded that these cells take up supplied sucrose only afterhydrolysis to hexoses, which are then absorbed by differentcarrier-mediated processes. Key words: Glucose, fructose, invertase, pea, protoplast, sucrose     

Regulators of Cell Division in Plant Tissues XIV. The Cytokinin Activities and Metabolism of 6-Acylaminopurines

Certain 6-acylaminopurines have been shown to exhibit activity in several cytokinin bioassays. The active compunds included 6-N,2′-O-dibutyryladenosine 3’:5′-cyclic monophosphate, but adenosine 3′:5′-cyclic monophosphate was inactive. The metabolites formed from [2,8-³H] 6-benzoylaminopurine by radish seedlings and excised radish cotyledons were investigated. When compared with zeatin, this amide showed considerable stability in vivo. Conversion to 6-benzylaminopurine and its riboside was not detected but slight degradation to adenine was indicated. The principal metabolite was an unidentified compund.     

Growth Response to Hormones by a New Rat Ovary Cell Line

SEVERAL endocrine cell lines established in recent years show a functional response to hormones in vitro¹ but, except for one mammary cell line², none of them exhibits the normal hormone requirement for growth in vivo. We have now isolated a rat ovarian cell line whose growth in vitro is markedly stimulated by bovine luteinizing hormone (LH-NIH-B7), a pituitary gonadotrophin and by dexamethasone, a synthetic glucocorticoid. This cell line provides the first permanent in vitro system for studying the growth stimulation of gonadal cells by hormones.     

Some Blood Sporozoans from East African Reptiles*

SYNOPSIS. Six hundred and forty-one lizards belonging to 28 species, and 29 snakes belonging to 12 species from East Africa were examined for blood sporozoans. Eight species of lizards and 4 of snakes were positive. Tissue phases were seen in some infections; no proven arthropod vectors were found. Parasites are described from previously unreported hosts; new host records, and new stages in the life histories of previously named parasites are reported. The sporozoans belong to the genera Plasmodium, Haemoproteus, Haemogregarina or Hepatozoon, and probably Pirhemocyton. Reasons are given for the inadvisability of establishing new species of some of these on the basis of blood stages alone.     

Muscle Plasticity During Sprouting and Reinnervation

SYNOPSIS. When peripheral nerves are cut, the axotomized nervesand denervated muscles undergo atrophic changes which are reversedonly when functional connections are remade in the periphery.The restored interaction completely reverses the effects ofaxotomy and denervation and leads to rematching of the sizeof the motoneuron, muscle unit force, speed and histochemicalproperties, according to the size principle. Differences inunit force and fatigue characteristics between motor unit typesare not fully restored in reinnervated muscles but do not obscuresize relationships between the motoneurons and their muscleunits. Although intact motoneurons will supply increased numbers ofmuscle fibers after partial nerve injuries, regenerating axonsappear to be limited in their ability to enlarge their muscleunits. Increased motor unit force in reinnervated slow motorunits is accounted for primarily by an increase in fiber diameter;fast motor units do not increase their mean force output. As a result of the rematching of muscle unit properties withthe size of the motoneurons that reinnervate them, motor unitproperties are appropriate for fine control of movement aftercomplete or partial nerve injuries. However, regenerating axonsdo not reinnervate their original muscle fibers and unless thefibers are injured close to the muscles, they often fail toreinnervate their original muscles. The mismatching of motorpools with inappropriate target muscles is probably the mainfactor responsible for poor recovery of motor function aftercomplete nerve injuries.     

Changes in Trifolium arvense Seed Quality Following Alternating Temperature Treatment using Liquid Nitrogen

The effects of alternating temperatures, using liquid nitrogen(–196°C) as the low temperature phase, on Trifolium arvense L.seed quality was investigated. Treatment reduced hardseedednesswith the seeds exhibiting a linear increase in the probit ofgermination with the logarithm of the number of alternatingtemperature cycles. Germination levels equal to ‘chipped’controls were achieved after four cycles or more, dependingon the initial depth of hardseededness, and the response wasunaffected by either the rate of cooling or the rate of warming. Imbibition time was reduced with increasing alternating temperaturecycles. Resealing experiments identified the main area of wateruptake as the lens, and SEM showed that deepening of alreadypresent cracks may be important in removing hardseededness.Pre-treatment of seeds with alternating temperatures predisposesthe seeds to subsequent damage by sulphuric acid treatment,but not by impaction. Stress effects were not restricted to the seed coat surfaceas between 10 and 20 % of seeds treated for 3–15 cyclesdeveloped into abnormal seedlings with detached cotyledons.Seed vigour is also reduced as treatment leads to contractionof the temperature response curve for germination. The resultshave implications for the cryopreservation of papilionoid legumeseeds as a means of genetic conservation. Trifolium arvense, Hare's foot, hardseededness, quantal response, cryopreservation, liquid nitrogen