Structure of saguaro cactus virus 3' translational enhancer mimics 5' cap for eIF4E binding

The genomes of several plant viruses contain RNA structures at their 3' ends called cap-independent translation enhancers (CITEs) that bind the host protein factors such as mRNA 5' cap-binding protein eIF4E for promoting cap-independent genome translation. However, the structural basis of such 5' cap-binding protein recognition by the uncapped RNA remains largely unknown. Here, we have determined the crystal structure of a 3' CITE, panicum mosaic virus-like translation enhancer (PTE) from the saguaro cactus virus (SCV), using a Fab crystallization chaperone. The PTE RNA folds into a three-way junction architecture with a pseudoknot between the purine-rich R domain and pyrimidine-rich Y domain, which organizes the overall structure to protrude out a specific guanine nucleotide, G18, from the R domain that comprises a major interaction site for the eIF4E binding. The superimposable crystal structures of the wild-type, G18A, G18C, and G18U mutants suggest that the PTE scaffold is preorganized with the flipped-out G18 ready to dock into the eIF4E 5' cap-binding pocket. The binding studies with wheat and human eIF4Es using gel electrophoresis and isothermal titration calorimetry, and molecular docking computation for the PTE-eIF4E complex demonstrated that the PTE structure essentially mimics the mRNA 5' cap for eIF4E binding. Such 5' cap mimicry by the uncapped and structured viral RNA highlights how viruses can exploit RNA structures to mimic the host protein-binding partners and bypass the canonical mechanisms for their genome translation, providing opportunities for a better understanding of virus-host interactions and non-canonical translation mechanisms found in many pathogenic RNA viruses.

Advances in chaperone-assisted RNA crystallography using synthetic antibodies

RNA molecules play essential roles in many biological functions, from gene expression regulation, cellular growth, and metabolism to catalysis. They frequently fold into three-dimensional structures to perform their functions. Therefore, determining RNA structure represents a key step for understanding the structure-function relationships and developing RNA-targeted therapeutics. X-ray crystallography remains a method of choice for determining high-resolution RNA structures, but it has been challenging due to difficulties associated with RNA crystallization and phasing. Several natural and synthetic RNA binding proteins have been used to facilitate RNA crystallography. Having unique properties to help crystal packing and phasing, synthetic antibody fragments, specifically the Fabs, have emerged as promising RNA crystallization chaperones, and so far, over a dozen of RNA structures have been solved using this strategy. Nevertheless, multiple steps in this approach need to be improved, including the recombinant expression of these anti-RNA Fabs, to warrant the full potential of these synthetic Fabs as RNA crystallization chaperones. This review highlights the nuts and bolts and recent advances in the chaperone-assisted RNA crystallography approach, specifically emphasizing the Fab antibody fragments as RNA crystallization chaperones.

Efficient aqueous molybdenum removal using commercial Douglas fir biochar and its iron oxide hybrids

Molybdenum (Mo) is a naturally-occurring trace element in drinking water. Most commonly, molybdate anions (MoO₄^2-) are in well water and breast milk. In addition, it is used in medical image testing. Recently, the EPA classified Mo as a potential contaminant, as exposure can lead to health effects such as gout, hyperuricemia, and even lung cancer. We have assessed the sorptive removal of aqueous molybdate using Douglas fir biochar (DFBC) and a hybrid DFBC/Fe₃O₄ composite containing chemically-coprecipitated iron oxide (Fe₃O₄). Adsorption was studied at various: pH values, equilibrium times (5 min-24 h), initial Mo concentrations (2.5-1000 mg/L), and temperatures (5, 25, and 40 °C) using batch sorption and fixed-bed column equilibrium methods. Langmuir capacities for DFBC and DFBC/Fe₃O₄ (at pH 3, 2 hrs equilibrium) were within 459.3-487.9 mg/g and 288-572 mg/g, respectively. These adsorbents and their Mo-laden counterparts were characterized by elemental analysis, BET, PZC, SEM, TEM, EDS, XRD, and XPS. MoO₄^2- adsorption on DFBC is thought to be governed primarily via electrostatic attraction. Adsorption by DFBC/Fe₃O₄ is primarily governed by chemisorption onto magnetite surface hydroxyl groups, while electrostatics prevail in the DFBC-exposed phase. Stoichiometric precipitation of iron molybdates triggered by iron dissolution was also considered. The data suggest that DFBC and DFBC/Fe₃O₄ are promising candidates for molybdate sorption.

Linear lesions in dermatology: a clinicoaetiopathological study

BACKGROUND

Linear lesions are fairly common in our daily practice. However, the appearance of these lesions can vary, thus complicating the diagnosis.

AIMS

To study the various clinical presentations, the demographic profile of patients and the clinicopathological correlations of dermatoses presenting with a linear distribution.

METHODS

We conducted an institution-based, cross-sectional, descriptive study of 281 consecutive patients with linear lesions attending dermatology clinics. MedCalc software (V11.6) was used for statistical analysis.

RESULTS

Patients were divided into eight groups: lesions along the lines of Blaschko (n = 136), lesions along blood vessels (n = 3), lesions along lymphatics (n = 3), Koebner phenomenon (n = 24), autoinoculation (n = 24), external factors (n = 45), infestations (n = 2) and 'other' (n = 44). The mean age at presentation was 24.50 ± 18.82 years and the male/female ratio was 1.32 : 1. The commonest symptom was itching/burning (56.94% of patients), while the commonest site was the arm (44.48%); followed by the leg (30.60%), trunk and abdomen (22.42%), head and neck (19.20%), and genitalia (0.35%). Apart from the common cases, there was a wide gamut of rare conditions (e.g. angiokeratoma circumscriptum naeviforme, porokeratotic eccrine ostial and dermal duct naevus, Blaschko-linear syringocystadenoma papilliferum, progressive cribriform and zosteriform hyperpigmentation, unilateral naevoid acanthosis nigricans, fixed drug eruption, discoid lupus erythematosus).

CONCLUSION

Linear lesions act as diagnostic clues to many dermatological conditions, therefore, the importance of meticulous examination in clinical dermatology cannot be overemphasized.

Catheter-related blood stream infections: prevalence, risk factors and antimicrobial resistance pattern

Background

Intravascular devices have significant potential for producing iatrogenic diseases resulting in catheter-related blood stream infections (CRBSIs). A study was undertaken to find the prevalence of CRBSI among patients in acute wards and to analyze the associated risk factors, causative pathogens with their antibiotic susceptibility (ABST) patterns.

Methods

Randomly ten days per month were chosen, for a period of two years. All the acute wards patients who were on indwelling blood catheters were identified. Those fulfilling the CRBSI criteria were further worked up for confirmation of diagnosis by differential time to positivity. The catheter tip was cultured by Maki's semiquantitative method. ABST of the isolates obtained was performed by Kirby-Bauer disk diffusion method.

Results

The prevalence of CRBSI was found to be 39.25% with the most common organism isolate being Serratia marcescens (23.81%). The immunocompromised status of the patients and catheterisation time were significant risk factors. Methicillin resistance was found to be 33.33% in coagulase-negative staphylococci. The resistance to vancomycin among the Entercoccus faecium isolates was found to be 33.33%. Among the gram negatives, resistance to aminoglycosides, fluoroquinolones and third-generation cephalosporins was high.

Conclusion

The study highlights the importance of regular surveillance programs, an efficient infection control program, strict adherence to antiseptic measures and use of a rational antibiotic policy for the early diagnosis and better management of CRBSI.

Drug sensitivity pattern of various Staphylococcus species isolated at a tertiary care hospital

BACKGROUND

Staphylococcus aureus and other Staphylococcus species are important pathogenic organisms and are responsible for various hospital infections. These are the predominant organisms found in pus and blood culture isolates. Infections arising due to these bacterial isolates are difficult to treat because of developing multidrug resistance.

METHODS

Over a 1-year period at a tertiary care hospital laboratory, 524 Staphylococci species were isolated from pus, blood and urine samples and species-level identification was done.

RESULTS

S. aureus formed the predominant species (70.8%) followed by coagulase-negative Staphylococcus (CoNS) (29.20%). S. aureus (91%) was the main isolate from pus samples; however, CoNS was isolated in equally higher proportion in blood culture (63.58%). Among the CoNS, Staphylococcus hemolyticus was the main isolate (9.3%). β-Lactamase production, alteration of PBP and MLSB resistance were seen in variable degrees in different species.

CONCLUSION

CoNS group of Staphylococci is becoming an important cause of infection at tertiary care centres. The increased multidrug resistance among various Staphylococcus species is a cause of great concern and requires adequate measures to prevent the spread of these microorganisms in the hospital and the community.

Density functional theory study of the effect of helium clusters on tritium-containing palladium lattices

Density functional theory (DFT) calculations have been employed to calculate the energetics, structures and migration behaviour of helium in palladium tritides. Increasing the tritium concentration in palladium leads to a decrease in the formation energies of helium clusters, indicating that He clusters can form in the lattices. The calculated results show less lattice expansion in Pd defect-containing lattices compared to the perfect lattice owing to smaller lattice distortions. The lowest energy migration path for helium diffusion is along octahedral-tetrahedral-octahedral sites but the energy barrier increases with increasing tritium concentration. Repulsive interactions occur between Pd d and He s orbitals, suggesting that displacement of the metal atoms in the lattice leads to growth of pressure inside the lattices. This process may change the microstructural properties leading to the degradation of the material.

Transvaginal sonography versus hysteroscopy in evaluation of abnormal uterine bleeding

BACKGROUND

Abnormal uterine bleeding (AUB) accounts for 33% of female patients referred to gynaecologists. Common causes of AUB include endometrial polyps, endometrial hyperplasia, submucous fibroids and anovulation. Accurate diagnosis of the cause of AUB can reduce the frequency of hysterectomy. This study was aimed at assessing the usefulness of TVS in comparison with hysteroscopy in AUB evaluation.

METHODS

100 female patients with AUB were enrolled in the study. Each patient was subjected to TVS where uterine cavity was studied in detail and hysteroscopy under anaesthesia using saline as distension medium. Sensitivity, specificity and predictive value of TVS as compared to hysteroscopy were calculated. Subgroup analysis within each group was also performed.

RESULTS

Menorrhagia was the commonest presenting symptom in the study population (n = 58) followed by metrorrhagia, menometrorrhagia and continuous bleeding >21 days. 74 female patients had normal size uterus. In 57 patients, the uterine cavity was normal on TVS. Thickened endometrium, endometrial polyp and submucous fibroids were seen in 19, 16 and 6 patients respectively. Hysteroscopy showed normal cavity in 59 female patients and polypoidal endometrium, polyps or submucous fibroids in 41. TVS was found to have high sensitivity and specificity (95.23 and 94.82 respectively) and high positive and negative predictive value. Strength of agreement between TVS and hysteroscopy was high (kappa value 0.898).

CONCLUSION

TVS is recommended as first line investigation in AUB. If TVS shows normal cavity, further evaluation can be omitted and patient started directly on medical treatment for her symptoms.

A rare case of gangrenous appendicitis by eggs of Taenia species

Cysticercosis and Taeniasis continue to be a major public health burden in the developing countries like India. Humans are the only definitive hosts infected by ingestion of eggs of Taenia species. Appendicular Taeniasis is rare with few isolated case reports during the past 30 years. Here, we report the case of a 38-year-old female patient from Nepal who presented with acute pain abdomen, was operated and diagnosed as suffering from gangrenous appendicitis caused by eggs of Taenia species.

Adolescent lumbar disc disease: findings and outcome

BACKGROUND

Lumbar disc herniation is mainly a disease of elderly people as degenerative changes progress with age.

RESULTS AND DISCUSSION

Present retrospective analysis was performed on 742 patients of lumbar disc disease operated over 11 years. Of 742 cases aged 20 years or less, 25 has been evaluated to see the clinical features, radiological features, operative findings, and outcome of lumbar disc surgery. The incidence of lumbar disc herniation in pediatric and adolescent populations was 3.5% (aged 20 years or less). All patients presented with low back pain with or without radiculopathy (n = 25). Diagnosis was easily made on magnetic resonance imaging. Gross degenerative changes in disc and end plates were uncommon (16%) in this population. The trauma may not be a predisposing factor in most of them. In 88% (n = 22) of the cases, only 1 level was affected; the commonest was L4-5 (n = 13). Disc herniation was centrolateral in 72% (n = 18) and central in 28% (n = 7). Disc was mostly soft, hydrated, and rubbery in 92% (n = 23). Disc herniation were subligamentous in 80% (n = 20) and extruded in 4% (n = 1). Sixteen percent (n = 4) of the patients had disc bulge with intact annulus.

CONCLUSIONS

Operative intervention in the form of simple discectomy offers good result in 92% (n = 23) cases irrespective of approach and method. Longer follow-up is mandatory because the chances of recurrence or another level involvement cannot be denied.

Reduction of mechanical heart valve thrombosis through a clinical audit

BACKGROUND AND AIM OF THE STUDY

Patients with mechanical heart valves implanted at four cardiothoracic centers were followed up in a hospital in Eastern India. Despite successful surgery and regular hospital visits, long-term survival was compromised by anticoagulation-related complications.

METHODS

Systematic analysis revealed under-anticoagulation in most patients. Thrombosis risk in 80 patients on regular follow up from 1989 to 1997 was 8.68 per 100 patient years (pt-yr). The incidence of both thrombotic and bleeding complications was reported as less than two per 100 pt-yr, when prothrombin time was consistently in the range of INR 2.5 to 3.9. In targeting this low event rate, impediments to optimum anticoagulation in the local set-up were identified. International Normalized Ratio (INR) was introduced to report prothrombin time (PT). Patients and doctors were educated about drug and diet interactions with oral anticoagulants (OAC) and the early features of valve thrombosis. Treatment protocols were evolved. The impact of the remedial measures was studied in 81 patients (64 old, 17 new) over a total of 254 pt-yr of follow up, from 1998 to 2001.

RESULTS

Thrombosis risk was reduced from 8.68 to 5.12 per 100 pt-yr, while non-fatal bleeding events increased from 0.28 to 1.96 per 100 pt-yr. Due to early recognition of occlusive prosthetic valve thrombosis and institution of fibrinolytic therapy, fatal events were reduced from 3.8 per 100 pt-yr to none for four consecutive years (statistically significant at 99% CI).

CONCLUSION

The clinical audit proved to be a valuable tool for understanding the problems in health care delivery, and bringing about improvement.

Renal artery involvement in patients of coronary artery disease undergoing coronary angiography--a prospective study

METHODS

We prospectively studied the angiographic incidence of renal artery stenosis in 1000 consecutive patients who underwent coronary angiography for clinically suspected coronary artery disease since December, 1998. Selective renal arteriography was performed in all the patients (mean age 57 years, 74.6% males) after coronary angiography.

RESULTS

Systemic arterial hypertension was present in 52%, 29.1% were smokers, 21% had diabetes and 31.2% had hypercholesterolemia. Significant coronary artery diseases was found in 849 (84.9%) patients. Of the total patient cohort, 103 (10.3%) patients had renal artery disease; 78 (7.8%) had insignificant stenosis (> 50%) and significant renal artery stenosis (< 50%) was identified in 25 (2.5%) patients. Three had bilateral renal artery stenosis. Comparisons were made between renal artery stenosis and risk factor profile. There was no statistically significant association between renal artery stenosis and parameters like diabetes mellitus, hypertension, smoking, lipid levels and serum creatinine.

CONCLUSION

In our study, the absolute number of cases with significant renal artery stenosis is small, so no statistical analysis could be performed to demonstrate the relationship of presence of renal artery stenosis with severity of CAD. However patients with severe coronary artery disease or having multiple risk factor showed a trend towards increased prevalence of renal artery stenosis, hence renal angiography should be done for this subset of patients.

Coronary stenting without pre-dilatation: an observational study

Conventional coronary stenting is done after pre-dilatation of the lesion. The bleeding complications and incidence of subacute stent thrombosis have been reduced significantly by the use of antiplatelet agents and high pressure balloon inflation to ensure complete stent expansion. Elective stenting also can be done without pre-dilatation by "stent alone technique." This approach significantly reduces the procedural cost and ischaemia time, avoiding potential complications such as abrupt vessel closure because of extensive dissection after conventional angioplasty and prior to stent deployment. Eighty patients of stable angina pectoris suitable for coronary angioplasty underwent stenting without pre-dilatation. Out of the 100 stents used, 38 were hand-crimped and 62 were pre-mounted. The target vessels were left anterior descending artery in 56 percent, right coronary artery in 32 percent and left circumflex in 12 percent. The procedure was successful in 88 percent lesions. In 12 percent stenting could be done only after pre-dilatation. In all these, there was proximal tortuosity and calcification. The fluoroscopy time was 10.2 +/- 4.5 minutes. The average number of balloons used per lesion was 1.08. Stent embolisation occurred in only one patient. There were no major adverse cardiac events in any of the patients. Thus stenting without pre-dilatation is safe. Patients who are eligible for stenting without pre-dilatation are those with stable angina pectoris without fluoroscopically visible calcium or coronary artery tortuosity and with lesions of moderate complexity.

Coil embolization of a giant atherosclerotic coronary artery aneurysm

The incidence of the coronary artery aneurysm varies from 1.5-5%. Atherosclerosis is the most common cause of coronary artery aneurysm in adults. A discrete, giant, saccular atherosclerotic coronary artery aneurysm in an artery without significant proximal stenosis is rare. We report the first such case of a giant atherosclerotic coronary artery aneurysm successfully treated with coil embolization.

Balloon mitral valvuloplasty with bifoil catheter: immediate and long-term follow-up results

This report documents clinical and hemodynamic benefits of balloon mitral valvuloplasty (BMV) using a bifoil balloon catheter from a single center in 415 consecutive cases of rheumatic mitral stenosis (MS). The procedure was successful in 396 (95.2%) patients, with an increase in mitral valve area (MVA) from 0.82+/-0.35 cm2 to 2.21+/-0.24 cm2 (P < 0.001). There were 2 (0.48%) in-hospital deaths, and 6 (1.44%) patients developed acute mitral regurgitation. The procedural and fluroscopy time was reduced significantly from 52+/-11 and 38+/-6 min to 33+/-7 and 19+/-5 min, respectively, after modifications of technique in our last 326 cases. The bifoil balloon catheter technique is safe and effective, and provides excellent hemodynamic benefits which are sustained at long-term follow-up. This technique should be considered as an addition to the existing armamentarium of interventional cardiologists performing mitral balloon valvuloplasty.

A University of California State-supported AIDS research award program--a unique state and university partnership in AIDS research

This article describes the State-supported University of California AIDS research award program and its major accomplishments. It shows how a partnership between a University and a State resulted in the formation of a successful, efficient, and cost-effective AIDS research award program. This program provides funds for rapid testing of investigator-initiated meritorious research ideas, new drugs, and treatment modalities. Funds were also utilized to establish three AIDS Clinical Research Centers, which evolved into regional consortia that coordinate trials of new drugs and other modalities. This program succeeded in involving investigators whose efforts have led to excellent medical care, advanced technologies, and new drugs for treating AIDS and AIDS-related diseases. The University remains committed to continuing support of all areas of AIDS research, emphasizing drug and vaccine development, pediatric AIDS, and AIDS prevention studies in groups at high risk for HIV infection.

Quantitative evaluation of peer review of program project and center applications in allergy and immunology

We compared the review patterns of applications for program projects and centers in allergy and immunology, reviewed by the National Institute of Allergy and Infectious Diseases review committee, with those of individual research projects in immunology, reviewed by three Division of Research Grants study sections. A high concordance between these review groups was obtained with respect to the application approval rate, mean score, and distribution of applications in various priority score ranges. Furthermore, we observed a high degree of consensus among reviewers on the quality of many program project and center applications, especially those with priority scores between 100 and 200.

In vitro susceptibility of Escherichia coli of swine origin to carbadox and other antimicrobials

Swine fecal Escherichia coli isolates were tested with the Microtiter broth dilution method for susceptibility to carbadox and 11 other antimicrobials. Of the 138 strains, 136 were resistant to sulfadiazine, 120 to tetracycline, 95 to streptomycin, and 63 to carbadox. Resistance to the remaining antimicrobials also was noted in various degrees, with the exception of amikacin, to which all strains were susceptible. Carbadox-resistant strains also were resistant to other antimicrobials. The multiple resistance pattern was most common to sulfadiazine and tetracycline or a combination of sulfadiazine, tetracycline, and streptomycin.

A note on fitness of haemoglobin genotypes in the Bengali-speaking population

In the Bengali-speaking population of Calcutta (India) the genotype frequencies of the Hb beta-A/E/T system are given. The fitness of the genotypes has been calculated. It is found that this system is not in stable or semistable equilibrium in this population.

A study on genetic selection and haemoglobin heterozygotes: Hb A/E and beta-thalassaemia trait

In this paper the genetic fitness of the two heterozygotes Hb A/E and β-thalassaemia trait, in Calcutta, is examined in terms of their reproductive performance. It is found from fertility that the heterozygote Hb A/E enjoys some selective advantage over the normal homozygote Hb A/A, but the other heterozygote (β-thalassaemia trait) does not. But from overall reproductive performance (fertility and infant mortality together) it is postulated that the heterozygotes will eventually suffer from a selective disadvantage in a place like Calcutta, where malaria was eradicated about three decades ago.

Histone patterns during early embryogenesis in the euchiuroid Urechis caupo

Histones were isolated from nuclei of Urechis caupo unfertilized eggs and embryos from early cleavage through gastrula. Polyacrylamide gel electrophoresis showed the presence of a slow migrating H1s fraction in the egg which was replaced by a faster migrating H1 during development. Radioactive labelling showed no synthesis of H1s from fertilization up to gastrula and a high rate of synthesis of H1 relative to the other histones during cleavage and blastula stages.

National Institute on Aging Mycoplasma Testing Service

The National Institute on Aging (NIA) has established a Mycoplasma Contamination Testing Service for NIA grantees studying cellular aging on cell-culture systems. The contractor is the Institute for Medical Research, Camden, New Jersey.

National Institute on Aging cell-line repository

The National Institute on Aging (NIA) has established, under contract, a cell-line repository. This resource is designed to support NIA grantees, prospective grantees, and other laboratories engaged in cellular aging research. Services of the NIA Cell-Line Repository include storage and distribution of characterized, contaminant-free normal diploid and genetically-marked human cell-lines.

Effect of ruminal lactic acid-utilizing bacteria on adaptation of cattle to high-energy rations

Heifers, unadapted to a concentrate ration, were intraruminally inoculated (1 dose) with cultures of ruminal lactic acid-utilizing bacteria or with ruminal fluid from a steer adapted to a concentrate ration. Inoculation with cultures (1 L) of Selenomonas ruminantium or Megasphaera elsdenii did not produce better average daily weight gains or feed efficiency of heifers fed a high-energy ration for 21 days, if these values were compared with the performance of noninoculated heifers. Average daily weight gain and feed efficiency of heifers inoculated with 1 L of Peptococcus asaccharolyticus culture or with 1 L of adapted ruminal fluid and fed a high-energy ration for 21 days were better if these values were compared with the performance of noninoculated heifers.

Lactic acid-utilizing bacteria in ruminal fluid of a steer adapted from hay feeding to a high-grain ration

A mature, rumen-cannulated steer fed Coastal Bermuda grass hay for 8 weeks was adapted to a high-grain ration by stepwise increases in grain over a period of 4 weeks. The grain rations had concentrate-to-roughage ratios of 40:60, 70:30, and 85:15 and were fed for 10, 7, and 11 days, respectively. Numerical estimates of lactate-utilizing bacteria in ruminal fluid of the steer the last 3 days each ration was fed were made by colony counts. Lactate-utilizing bacteria were identified as Megasphaera elsdenii, Peptococcus asaccharolyticus, and Selenomonas ruminantium. Maximal numbers of lactate-utilizing bacteria were observed in the ruminal fluid of the steer during feeding the concentrate-to-roughage ration of 70:30.

Mitotic chromosome condensation in the sperm nucleus during postfertilization maturation division in Urechis eggs

Changes in the morphology of the sperm nucleus in the egg cytoplasm are mong the immediate events in nucleocytoplasmic interactions during early embryogenesis. Soon after its entrance into the egg cytoplasm, the sperm nucleus of various organisms increases in size with the transformation of condensed chromatin to a diffuse state, resembling the chromatin of an interphase nucleus (2, 13, 15, 16). This is followed by a close association or fusion of male and female pronuclei (2, 13, 15, 16). Cytoplasmic influences on nuclear morphology have also been demonstrated clearly in nuclear transplantation and cell fusion studies (10, 11). Reactivation of the nucleus, such as the transplanted brain nucleus in Xenopus egg cytoplasm or the hen erythrocyte nucleus in interphase cytoplasm of HeLa cells, is accompanied by nuclear enlargement and chromatin dispersion (10, 11). However, premature mitotic-like chromosome condensation takes place in the nuclei of sperm or interphase cells fused with mitotic cells (9, 12). Thus, chromosome dispersion and condensation seem to depend on the state of the cytoplasm in which the nucleus is present. These observations imply that the initial morphological changes in the sperm nucleus after fertilization may very well be dependent on the state of maturation of eggs at the time of sperm entry. Unfertilized eggs of Urechis caupo, a marine echiuroid worm, are stored at the diakinesis stage. These eggs complete maturation division after insemination and this is followed by fusion of male and female pronuclei (5, 8). Therefore, Urechis caupo is a suitable organism in which to study the response of the sperm nucleus to the changing state of the egg cytoplasm during and after postfertilization maturation division.

Prenucleolar Bodies of Urechis Oocytes

The immature oocyte and unfertilized eggs of Urechis caupo, a marine echiuroid worm, contain many nuclear bodies and a main nucleolus. These bodies are similar to prenucleolar bodies of other materials with respect to their origin, structure, cytochemical and biochemical characteristics. They are formed in large numbers during the diffuse diplotene stage, perhaps by an aggregation of nucleolar materials which had been associated with chromosomes. They are fibrillar in structure, made up mainly of some nucleolar proteins, and are inactive in RNA synthesis. Biochemical analyses suggest the possibility that these structures contain a small amount of ribosomal RNA precursors which may have originated from the main nucleolus. An accumulation of prenucleolar bodies in Urechis oocytes may result from the lack of formation of multiple functional nucleoli, such as those found in amphibian oocytes.

Sites of synthesis and processing of ribosomal RNA presurosrs within the nucleolus of Urechis caupo eggs

Nucleoli from unfertilized Urechis eggs, labeled with tritiated RNA precursors, have been isolated for simultaneous autoradiographic localization and biochemical analysis of labeled RNA. The production of the ribosomal RNA precursor (38S) and its first cleavage occur at the fibrillar core region of the nucleolus. The products, predominantly 30S RNA, are then rapidly transported and stored in the granular cortex of the nucleolus. The formation of the nucleolar cortex, therefore, seems to result from an accumulation of partially processed ribosomal RNA with its associated proteins.

Chemotherapy of mice experimentally infected with Shigella flexneri

A chronic infection with Shigella flexneri 2a has been established in mice for the evaluation of compounds for therapeutic potential. Evidence of infection is indicated by prolonged symptomless excretion in the feces and by positive isolation of organisms from different segments of the intestinal tract and from mesenteric lymph nodes. Serum antibody titer reaches a maximum after 9 days of infection and remains at a low level until 32 days postinfection. In this model, five drugs used in human shigellosis were evaluated for efficacy. Ampicillin was found to be the most active followed by oxytetracycline and kanamycin. Neomycin and colistin were the least active in this system.

Binding of labeled ribonucleic acid to basic proteins, a major diffic- ulty in ribonucleic acid-deoxyribonucleic acid hybridization in fixed cells in situ

In an attempt to hybridize H3-ribonucleic acid (RNA) of onion roots to deoxyribonucleic acid of fixed cells in situ it has been found that such RNA binds only to cytoplasmic basic proteins (ribosomal?) as well as nuclear histones or protamines of diverse plant and animal materials. The bound RNA is relatively insensitive to mild RNase digestion. Most of these basic proteins cannot be removed from cells without distorting cell morphology, or without the prior removal of deoxyribonucleic acid. The binding characteristics of H3-RNA and basic proteins parallel alkaline fast green staining of histones. In the formalin-fixed cells, H3-RNA binds to the nucleus only after removal of deoxyribonucleic acid. The binding capacity is abolished after acetylation or deamination of lysine-rich histones; such treatments do not affect the binding ability of arginine-rich histones or protamines.

Evidence for control of the rate of nuclear DNA synthesis by the nuclear membrane in eukaryotic cells

Rates of DNA synthesis in root tip cells of diploid and autotetraploid snapdragon (Antirrhinum majus) seedlings and in diploid and tetraploid (mononucleate and bidiploid-nucleate) regenerating mouse-liver cells have been studied. The increase in this rate in the tetraploid cells is closely correlated with the increase in nuclear surface area, but not with the nuclear volume; this suggests a possible control of the rate of DNA synthesis by the nuclear membrane.

Effects of Supplemental Calcium or Calcium-binding Agents on Staphylococcal Bacteriophage Proliferation in Skim Milk

Additions of 0.0005 N calcium borogluconate to Trypticase Soy Broth (TSB) produced an increase in phage titer about 1 million-fold, whereas its addition to skim milk resulted in about a 100-fold decrease in the maximal titer. Supplemental calcium had a stimulatory influence on bacterial growth in TSB but not in skim milk. Studies were made of the effect of binding of calcium of skim milk on the proliferation of staphylococcal bacteriophage. Sequestering the calcium with 2% phosphate mixture inactivated the phages without affecting the bacterial growth. However, chelation of calcium by 0.012% ethylenediaminetetraacetic acid produced an inhibitory effect on both the phages and the bacteria.

Adsorption of staphylococcal bacteriophage by milk proteins

Propagation of homologous bacteriophage in a culture of Staphylococcus aureus (1:1 ratio of phage to bacteria) in Trypticase Soy Broth (TSB) and in skim milk indicated more activity of phage in TSB. Early lysis of bacteria in skim milk followed by a pronounced rise in bacterial population suggested that staphylococcal phages were being inactivated by milk. Titration of phages from skim milk, whey, and TSB indicated about 90% adsorption of phages by acid- and heat-precipitable proteins of skim milk, whereas numbers recovered from whey were quite comparable to those recovered from TSB. Reducing the pH from 6.5 to 4.0 increased the percentage of phages recoverable from skim milk from 10 to 56%. Apparently, the changes in electrical charges on the casein micelles at this low pH were responsible for release of many phages from their complex with casein.