Facilitators and barriers to adolescent participation in a TB clinical trial

BACKGROUND

The inclusion of adolescents in TB drug trials is essential for the development of safe, child-friendly regimens for the prevention and treatment of TB. TB Trials Consortium Study 31/AIDS Clinical Trials Group A5349 (S31/A5349) enrolled adolescents as young as 12 years old. We assessed investigator and coordinator described facilitators and barriers to adolescent recruitment, enrollment, and retention.

METHODS

Interviews were conducted with six investigators from sites that enrolled adolescent participants and six investigators from non-enrolling sites. Additionally, two focus groups were conducted with study coordinators from enrolling sites and two focus groups with non-enrolling sites. Discussions were transcribed, analyzed, summarized, and summaries were reviewed by Community Research Advisors Group members and research group representatives for content validity.

RESULTS

Investigators and coordinators attributed the successful enrollment of adolescents to the establishment and cultivation of external partnerships, flexibility to accommodate adolescents' schedules, staff engagement, recruitment from multiple locations, dedicated recruitment staff working onsite to access potential participants, creation of youth-friendly environments, and effective communications. Non-enrolling sites were mainly hindered by regulations. Suggestions for improvement in future trials focused on study planning and site preparations.

CONCLUSION

Proactive partnerships and collaboration with institutions serving adolescents helped identify and reduce barriers to their inclusion in this trial..

Factors associated with mortality in patients with COVID-19 admitted to intensive care: a systematic review and meta-analysis

Identification of high-risk patients admitted to intensive care with COVID-19 may inform management strategies. The objective of this meta-analysis was to determine factors associated with mortality among adults with COVID-19 admitted to intensive care by searching databases for studies published between 1 January 2020 and 6 December 2020. Observational studies of COVID-19 adults admitted to critical care were included. Studies of mixed cohorts and intensive care cohorts restricted to a specific patient sub-group were excluded. Dichotomous variables were reported with pooled OR and 95%CI, and continuous variables with pooled standardised mean difference (SMD) and 95%CI. Fifty-eight studies (44,305 patients) were included in the review. Increasing age (SMD 0.65, 95%CI 0.53-0.77); smoking (OR 1.40, 95%CI 1.03-1.90); hypertension (OR 1.54, 95%CI 1.29-1.85); diabetes (OR 1.41, 95%CI 1.22-1.63); cardiovascular disease (OR 1.91, 95%CI 1.52-2.38); respiratory disease (OR 1.75, 95%CI 1.33-2.31); renal disease (OR 2.39, 95%CI 1.68-3.40); and malignancy (OR 1.81, 95%CI 1.30-2.52) were associated with mortality. A higher sequential organ failure assessment score (SMD 0.86, 95%CI 0.63-1.10) and acute physiology and chronic health evaluation-2 score (SMD 0.89, 95%CI 0.65-1.13); a lower PaO₂ :F_I O₂ (SMD -0.44, 95%CI -0.62 to -0.26) and the need for mechanical ventilation at admission (OR 2.53, 95%CI 1.90-3.37) were associated with mortality. Higher white cell counts (SMD 0.37, 95%CI 0.22-0.51); neutrophils (SMD 0.42, 95%CI 0.19-0.64); D-dimers (SMD 0.56, 95%CI 0.43-0.69); ferritin (SMD 0.32, 95%CI 0.19-0.45); lower platelet (SMD -0.22, 95%CI -0.35 to -0.10); and lymphocyte counts (SMD -0.37, 95%CI -0.54 to -0.19) were all associated with mortality. In conclusion, increasing age, pre-existing comorbidities, severity of illness based on validated scoring systems, and the host response to the disease were associated with mortality; while male sex and increasing BMI were not. These factors have prognostic relevance for patients admitted to intensive care with COVID-19.

Risk factors and interventions associated with mortality or survival in adult COVID-19 patients admitted to critical care: a systematic review and meta-analysis

Background: Patients with confirmed COVID-19 admitted to intensive care units have a high mortality rate, which appears to be associated with increasing age, male sex, smoking history, hypertension and diabetes mellitus. Methods: A systematic review to determine risk factors and interventions associated with mortality/survival in adult patients admitted to an intensive care unit (ICU) with confirmed COVID-19/SARS-CoV-2 infection. The protocol was registered with PROSPERO (CRD42020181185). Results: The search identified 483 abstracts between 1 January and 7 April 2020, of which nine studies were included in the final review. Only one study was of low bias. Advanced age (odds ratio [OR] 11.99, 95% confidence interval [CI] 5.35–18.62) and a history of hypertension were associated with mortality (OR 4.17, 95% CI 2.90–5.99). Sex was not associated with mortality. There was insufficient data to assess the association between other comorbidities, laboratory results or critical care risk indices and mortality. The critical care interventions of mechanical ventilation (OR 6.25, 95% CI 0.75–51.93), prone positioning during ventilation (OR 2.06, 95% CI 0.20–21.72), and extracorporeal membrane oxygenation (ECMO) (OR 8.00, 95% CI 0.69, 92.33) were not associated with mortality. The sample size was insufficient to conclusively determine the association between these interventions and ICU mortality. The need for inotropes or vasopressors was associated with mortality (OR 6.36, 95% CI 1.89–21.36). Conclusion: The studies provided little granular data to inform risk stratification or prognostication of patients requiring intensive care admission. Larger collaborative research is needed to address this limitation.

Prevalence and patterns of victimization and polyvictimization among female sex workers in Soweto, a South African township: a cross-sectional, respondent-driven sampling study

Background: Female sex workers (FSWs) are disproportionately affected by violence from multiple partner categories. This increases their vulnerability to HIV.

Objectives: To describe patterns of violence and polyvictimization among female SWs in Soweto.

Methods: A respondent-driven sampling (RDS) recruitment methodology was used to enrol 508 Soweto-based FSWs using a survey instrument. Raw and RDS adjusted data were descriptively analysed, Spearman’s correlation and chi² test of association were used to show associations. Polyvictimization patterns are shown within a modified Venn diagram.

Results: The median age of FSWs in Soweto was 31 years, and most had an incomplete education (74.2%). The prevalence of exposure to physical/sexual intimate partner violence (IPV) in the past year was 53.8%, 46.8% by clients, and 18.5% by police. Past year prevalence of sexual/physical violence by any perpetrator category was 70.8% and lifetime exposure was 76.0%. Childhood sexual violence was reported by 44.3%. Lifetime non-partner rape was 55.5% and all rape exposure was 62.4%. As a result of engaging in sex work in the past year, 65.2% women had been discriminated against. Client, police, IPV, and childhood trauma were all significantly associated with one another, with IPV being the most common co-occurrence. Polyvictimization was seen in almost two-thirds of FSWs, and increased with exposure to discrimination.

Conclusion: In Soweto, FSWs are exposed to high rates of violence in multiple forms across their lifetime. Our findings show that violence continues unabated into adulthood at levels far higher than in the general population and overall at higher levels than previously recorded among SWs in South Africa. We argue that violence against FSWs is rooted in discrimination. The disparate burden of violence on FSWs requires urgent interventions to proactively address and reframe the normalisation of violence against all women.

Variation in water disappearance, daily dose, and synovial fluid concentrations of tylvalosin and 3-O-acetyltylosin in commerical pigs during five day water medication with tylvalosin under field conditions

Tylvalosin (TVN) is a water soluble macrolide used in swine production to treat enteric, respiratory, and arthritic pathogens. There is limited data on its distribution to synovial fluid beyond gavage studies, which do not represent field conditions. This study measured water disappearance, TVN concentration in the medicated water, daily dose, and concentrations of TVN and 3-O-acetyltylosin (3AT) in the synovial fluid and plasma of treated pigs over the administration period. The study emphasized understanding variation in tissue TVN concentrations within the context of a field setting. Sixty finisher pigs were housed individually with individual waterers. Six pigs were randomly allocated to the following time points for sample collection: 0, 48, 60, 72, 84, 96, 102, 108, 114, and 120 hr on medication. TVN was administered daily in the water for 5 days. Water disappearance and medicated water concentration were measured daily. At each time point, six pigs were euthanized and plasma and synovial fluid were collected for analysis. Median TVN synovial fluid concentrations ranged between <1 ng/ml (hour 0) to 3.6 ng/ml (hour 84). There was substantial variation between individual pigs for water disappearance (mean 4.36L and range 0-7.84). Median TVN water concentration was 59 ppm (range 38-75 ppm).

Concentrations of tylvalosin and 3-O-acetyltylosin attained in the synovial fluid of swine after administration by oral gavage at 50 and 5 mg/kg

The objectives of this study were to determine the concentration of tylvalosin (TVN) and its metabolite, 3-O-acetyltylosin (3AT) in the synovial fluid of growing pigs when administered as a single bolus by oral gavage at target doses of 50 mg/kg (Trial 1) and 5 mg/kg (Trial 2). TVN is a water soluble macrolide antimicrobial used in swine production. The stability of the drug in synovial fluid samples stored at -70 °C up to 28 days was also evaluated in Trial 2. In Trial 1, eight pigs were randomly assigned to one of eight time points for euthanasia and synovial fluid collection: 0, 1, 2, 3, 4, 6, 9, 12 h postgavage. For Trial 2, 24 pigs were randomly allocated to one terminal collection time point at 0, 2, 4, 6, 8 or 10 h postgavage. Synovial fluid was analyzed to determine TVN and 3AT concentrations. TVN and 3AT were detected in Trial 1 at all time points, except 0 h. At 2 h postgavage for trial 2, the mean concentrations peaked at 31.17 ng/mL (95% CI: 18.62-52.16) for TVN and at 58.82 ng/mL (95% CI: 35.14-98.46) for 3AT. Storage duration did not impact TVN or 3AT concentrations (P-value 0.9732).

Loss to follow-up among infants in a study of isoniazid prophylaxis (P1041) in South Africa

OBJECTIVE

To assess risk factors for loss to follow-up (LFU) from the IMPAACT P1041 study, an isoniazid (INH) prophylaxis study conducted in southern Africa.

DESIGN

Infants in two cohorts, human immunodeficiency virus-infected (HIV+) and HIV-exposed but non-infected (HIV-), were randomized to INH or placebo for 96 weeks. LFU was evaluated at week 96.

RESULTS

Of 1351 infants, 12.9% were LFU (10.4% HIV+, 14.7% HIV-); 65% of the HIV+ cohort was asymptomatic. Among HIV+ infants, large household size (>6 vs. <4 members, P = 0.035) and presence of an elder (≥55 years, P = 0.05) were associated with better retention. Although attenuated in adjusted analysis, these associations held among HIV- infants. Among HIV- infants, having a younger mother increased the risk (P = 0.008) and maternal history of TB reduced the risk of LFU, the latter by nearly 70% (P = 0.048 univariate, 0.09 adjusted). LFU was largely due to inability to contact the participant (58% HIV+, 30% HIV-), and inability to attend the clinic and withdrawal of consent (HIV-).

CONCLUSIONS

Household support was an important factor in participant retention, particularly for the non-HIV-infected cohort, as young maternal age was a risk factor for LFU. Retaining study participants from this mobile population can be challenging and may warrant additional support.

NDM-1 has arrived: first report of a carbapenem resistance mechanism in South Africa

The New Delhi Metallo-β-lactamase (NDM) resistance mechanism in Enterobacteriaceae threatens to render serious Gram-negative infections untreatable. The NDM-1 enzyme hydrolyses all available penicillin, cephalosporin and carbapenem antibiotics, and is commonly accompanied by additional resistance mechanisms to multiple antibiotic classes. Initially identified as a significant healthcare risk on the Indian sub-continent, it has rapidly become a global problem, posing significant diagnostic and management challenges. Here we report the first laboratory-confirmed case of NDM-1 in South Africa.

A window into a public program for prevention of mother to child transmission of HIV: evidence from a prospective clinical trial

OBJECTIVES: To evaluate efficacy of the antenatal, intra-partum and post-natal antiretroviral components of a public service Prevention of Mother to Child (MTCT) program in infants. DESIGN: Analysis of prospectively collected screening data of demographic and MTCT-related interventions and HIV-infection status of infants identified through HIV-specific DNA polymerase chain reaction. SETTING: Tygerberg Children's Hospital, Western Cape Province, South Africa. SUBJECTS: HIV-infected women and their infants identified through participation in a public service MTCT program were referred for possible participation in a prospective study of isoniazid prophylaxis. INTERVENTIONS: Key components of the Program include voluntary counselling and testing, zidovudine to the mother from between 28 and 34 weeks gestation and to the newborn infant for the first week, single dose nevirapine to the mother in labour and the newborn shortly after birth and free formula for 6 months. MAIN OUTCOME MEASURES: Number and percentage of HIV-infected infants and extent of exposure to antenatal, intrapartum and post-natal antiretrovirals. RESULTS: Of 656 infants with a median age of 12.6 weeks, screened between April 1(st) 2005 through May 2006, 39 were HIV-infected giving a transmission rate of 5.9% (95% CI: 4.4% - 8.0%). Antenatal prophylaxis was significantly associated with reduced transmission (OR: 0.43 (95% CI: 0.21 - 0.94)) as opposed to intrapartum and postpartum components (p=0.85 and p=0.84, respectively). In multivariable analysis the antenatal component remained significant (OR=0.40 (95% CI 0.19 - 0.90)). CONCLUSIONS: The antenatal phase is the most important antiretroviral component of the MTCT program, allowing most opportunity for intervention.

Tuberculosis exposure in HIV-exposed infants in a high-prevalence setting

Exposure to TB was quantified by screening human immunodeficiency virus (HIV) exposed infants aged 3-4 months for an isoniazid prophylaxis study where tuberculosis (TB) exposure excluded enrolment. Seventy-seven (10.1%, 95%CI 8.0-12.4) of 766 infants had contact with a TB source case. Nurses and lay counsellors identified 52 infants during pre-screening and doctors identified 25 during formal screening. High exposure may contribute to high rates of TB in HIV-exposed infants. Programs to prevent mother-to-child transmission of HIV offer an important opportunity to screen for TB. In-depth assessment is required for evaluating TB exposure.

Structure and stereochemistry of triflavanoids containing both ether and carbon-carbon interflavanyl bonds

The first triflavanoids with both C-C and C-O-C interflavanyl bonds, epioritin-(4beta-->6)-epioritin-(4alpha-->4)-epioritin-4beta-ol, epioritin-(4beta-->3)-epioritin-(4beta-->6)-epioritin-4beta-ol and epioritin-(4beta-->3)-epioritin-(4beta-->6)-epimesquitol-4alpha-ol, were identified in the heartwood of Acacia caffra. The ethereal interflavanyl bond is readily susceptible to reductive cleavage with sodium cyanoborohydride in trifluoroacetic acid/dichloromethane which hence permits the unequivocal assignment of the absolute configuration of constituent flavanyl units.

Genetic variances for liveweight and fleece traits in Merino, Dohne Merino and South African Meat Merino sheep

(Co)variance estimates for weaning weight, yearling liveweight, clean fleece weight and fibre diameter at yearling age were obtained for Merino, Dohne Merino and South African Meat Merino flocks maintained on the same property. Direct additive genetic variances for weaning weight [expressed as a ratio of the total phenotypic variance (h2, direct heritability)] were estimated at 0.15 for Merinos, 0.21 for Dohne Merinos and 0.32 for South African Meat Merinos. Corresponding maternal variance ratios (m2, including direct maternal variance and permanent environmental maternal variance) were estimated at 0.15, 0.30 and 0.24, respectively. The correlation between direct and maternal variance ratios was high and negative in Dohne Merinos and South African Meat Merinos (–0.72 and –0.53, respectively). Direct heritability estimates for yearling liveweight were 0.30 for Merinos, 0.33 for Dohne Merinos and 0.45 for South African Meat Merinos. Corresponding maternal variance ratios were only significant in the latter 2 breeds, amounting to 0.13 in Dohne Merinos and 0.12 in South African Meat Merinos. For yearling clean fleece weight, h2 and m2 were estimated at 0.28 and 0.12, respectively, for both Merinos and Dohne Merinos. In the case of South African Meat Merinos, only the h2 estimate was significant, at 0.68. Maternal variance ratios for yearling fibre diameter were not significant in any of the breeds, while h2 ranged from 0.58 in Merinos to 0.75 in South African Meat Merinos. Selection progress for yearling traits seems likely in all breeds, depending on the breeding objectives being strived for.

Structure and synthesis of ether-linked proteracacinidin and promelacacinidin proanthocyanidins from Acacia caffra

Two new ether-linked proanthocyanidins, epioritin-(4beta-->3)-epioritin-4beta-ol and epimesquitol-(4beta-->4)-epioritin-4beta-ol, were isolated from the heartwood of Acacia caffra. Their structures and absolute configurations were established by spectroscopic methods and syntheses.

Structure and synthesis of the first procassinidin dimers based on epicatechin, and gallo- and epigallo-catechin

The range of natural dimeric procassinidins is extended by identification of cassiaflavan-(4alpha-->8)-epicatechin, cassiaflavan-(4alpha 8)-epigallocatechin, cassiaflavan-(4beta-->8)-epicatechin, cassiaflavan-(4beta-->8)-epigallocatechin, cassiaflavan-(4beta-->8)-gallocatechin, ent-cassiaflavan-(4beta-->8)-epicatechin and cassiaflavan-(4alpha-->6)-epicatechin in the bark of Cassia petersiana. Their structures and absolute configuration were confirmed by synthesis.

Disaggregation of aggregated platelets by apyrase from the tick, Ornithodoros savignyi (Acari: Argasidae)

Apyrase, secreted by ticks during feeding, is a platelet aggregation inhibitor that functions as a regulator of the host's hemostatic system. This present study concerns the disaggregation effect of salivary gland apyrase from the tick Ornithodoros savignyi. Secondarily aggregated platelets, disaggregated by apyrase, exhibited a reversal of shape from a spherical (aggregated) form to a discoid form, reminiscent of reversible aggregation at low ADP concentrations in citrated platelet-rich plasma. However, they showed a dilatory open canaliculary system and an absence of granules indicating disaggregation after degranulation had taken place. In contrast, disaggregation by the fibrin(ogen)olytic enzyme, plasmin, showed that platelets degranulated, but retained a spherical form with numerous extended pseudopods. While thrombin had no effect on aggregation or clotting of platelets disaggregated with plasmin, it did activate those platelets disaggregated with apyrase and clotted the plasma. This is the first study to describe the disaggregating effects of tick derived apyrase on aggregated platelets. It also shows that apyrase can disaggregate platelets even after secondary aggregation and degranulation of platelets has taken place. Platelet aggregation is one of the main barriers encountered by ticks during feeding and counteraction of this process by ticks is an important factor for successful feeding.

Anesthetic modulation of myocardial ischemia and reperfusion injury in pigs: comparison between halothane and sevoflurane

PURPOSE

Halothane offers protection against the reperfusion injury of the myocardium. This study compared sevoflurane with halothane in its potential to modulate the effects of acute severe ischemia and reperfusion on the myocardium.

METHODS

Experiments were conducted on 25 pigs. Anesthesia consisted of thiopental, vecuronium and fentanyl. The lungs were mechanically ventilated with oxygen and nitrogen. Animals were randomly allocated to receive either I MAC halothane or sevoflurane. A control group received fentanyl and pentobarbital. Regional myocardial function was measured with sonomicrometers. The left anterior descending coronary artery was occluded for 15 min followed by 60 min reperfusion.

RESULTS

Neither halothane nor sevoflurane protected the heart against the effects of acute and severe regional myocardial ischemia. During reperfusion, 89% of the animals receiving sevoflurane suffered from ventricular fibrillation compared with 30% in the halothane group (P < 0.005). Five minutes into the reperfusion period the animals subjected to halothane anesthesia demonstrated an 88% recovery in regional myocardial systolic function while in the sevoflurane group the recovery was 40% of pre-ischemic control (P < 0.05).

CONCLUSION

Halothane is associated with less reperfusion arrhythmias and, in addition, recovery of regional myocardial function during reperfusion was more rapid in the presence of halothane than with sevoflurane.

Subcellular localization of the nonstructural protein NS3 of African horsesickness virus

The subcellular localization of the minor nonstructural protein NS3 of African horsesickness virus (AHSV) has been investigated by means of immunogold electron-microscopical analysis. NS3 was observed in perturbed regions of the plasma membrane of AHSV-infected VERO cells, and its presence appears to be associated with events of viral release. These events are budding, whereby released viruses acquire fragments from the host-cell membrane, as well as by the extrusion of nonenveloped particles through the cell membrane. The membrane association of NS3 was confirmed by its detection in the disrupted plasma membranes of cells infected with an NS3 baculovirus recombinant. The absence of NS3 on intact cell membranes suggests that the protein is not exposed extracellularly.

Immunogold localization and quantification of cellular and subcellular abscisic acid, prior to and during drought stress

An immunogold labeling procedure and experimental data are presented, which demonstrate that antibodies produced against a bovine serum albumin-abscisic acid conjugate can be used both to characterize the cellular and subcellular localization of abscisic acid (ABA), and to permit quantitative comparisons of this hormone in the subcellular compartments prior to and at times of drought stress. At the control leaf water potential (approximately -0.45 MPa), a quantitatively similar positive labeling pattern was observed in the chloroplasts and apoplast. A twofold drought stress-induced increase in the apoplastic ABA concentration was observed in the drought stressed leaf tissue (i.e., at a leaf water potential of approximately -1.55 MPa), while the ABA concentration in the chloroplasts did not differ from that of the controls. Three histochemical controls and the physiological observations validated the specificity of the procedure. Based on the labeling patterns we observed and literature cited, the validity of the hypothesis that drought stress induces a release of chloroplastic ABA is questioned. We interpreted our results as providing indirect evidence for a drought stress-induced root source origin for the increased apoplastic ABA concentrations.

The localization of a paralysis toxin in granules and nuclei of prefed female Rhipicephalus evertsi evertsi tick salivary gland cells

A monoclonal antibody directed against a paralysis toxin of Rhipicephalus evertsi evertsi ticks was used to localize the toxin in cytoplasmic granules and, surprisingly, chromatin of the nuclei of cells which resemble the "b" cell type in the salivary glands of Rhipicephalus appendiculatus, Boophilus microplus and Ixodes holocyclus. The association of toxin with chromatin indicates that the toxin may have a regulatory function. Evidence is provided to support the view that the toxin is made up of three identical sub-units, with only the trimeric form being toxic.

Cryo-SEM evaluation of desiccation-sensitive dental specimens

As a result of desiccation, conventionally prepared fresh dental specimens, examined with the scanning electron microscope (SEM), exhibit obvious artifactual effects that may include one or more of the following: distortion, fracture, separation of structures, and chemical interactions. Cryo-SEM techniques reduce or eliminate these artifacts and present reliable images while requiring less time to perform than do conventional methods.

Plasmodium falciparum: isolation of intact and erythrocyte-free trophozoites from sorbitol lysates

An in vitro culture of Plasmodium falciparum (isolate FCUP-1/RSA) was arrested in the trophozoite stage with alpha-difluoromethylornithine (DFMO), followed by sorbitol treatment to liberate intracellular parasites from infected erythrocytes. Most of the unlysed erythrocytes and ghost membranes were removed by filtration, after agglutination with anti-erythrocyte monoclonal antibodies or wheat-germ agglutinin. A highly purified parasite preparation was obtained after chromatography on an immuno-affinity column consisting of polystyrene particles to which anti-erythrocyte monoclonal antibodies had been adsorbed. Isolated parasites were free of surrounding erythrocyte membranes and structurally intact as assessed by transmission electron microscopy, SDS-PAGE and ELISA.

The bent-leg syndrome in sheep. II. Association with genetic markers

Comprehensive blood typing (17 factors) and electrophoretic protein markers (haemoglobins, transferrins and albumins) were determined on S.A. Mutton Merino sheep (n = 275). The frequencies of these genetic markers were compared between ram lambs with normal and ram lambs with bent-legs and in a second trial between non-affected ewes and their lambs and ewes and lambs which were considered to be carriers of genetic factors resulting in the bent-leg syndrome. The presence of blood factors 2, 3 and 13 and the absence of factors 8, 10 and 17 is possibly linked to the bent-leg syndrome. Although the frequencies of TFA and TFD alleles were higher in the suspected carrier animals than non-affected animals, no definite linkage to the bent-leg syndrome was found. Haemoglobin and albumin type showed no correlation with the bent-let syndrome.

The bent-leg syndrome in sheep. I. The effect of pregnancy and age of the ewe on concentrations of plasma minerals

The effect of age of the ewe and pregnancy on concentrations of plasma calcium, phosphorus and magnesium and its relationship to the bent-leg syndrome in lambs, were investigated. This study included Merino ewes (n = 74), Dohne Merino ewes (n = 127), S A Mutton Merino ewes (n = 123) and S A Mutton Merino lambs (n = 145). Over a period of 8 years, 52 S A Mutton Merino ram lambs out of a total of 602 ram lambs weaned (8,6%), developed the bent-leg syndrome compared to the 2 ewe lambs out of 591 ewe lambs (0,3%) weaned. It was found that both the age of the ewe and pregnancy had no contributing effect in the development of this syndrome. The ewes of which the offspring developed the bent-leg syndrome, had an inverse plasma Ca:P ratio. Approximately 15% of the S A Mutton Merino ewes which gave birth to offspring which developed the bent-leg syndrome, had more than one lamb which developed this condition over the past 8 years. It is suggested that these ewes are carriers of certain genetic factors which can cause excessive phosphorus absorption. No differences in the concentration of plasma calcium, phosphorus and magnesium were found between ewe and ram lambs.

Effect of various propofol plasma concentrations on regional myocardial contractility and left ventricular afterload

The cardiovascular effects of propofol infusions, designed to maintain constant plasma concentrations, were examined in an open-chested pig model. Regional myocardial contractility was measured with the end-systolic pressure-length relationship (Ees) and left ventricular afterload quantified by the effective arterial elastance (Ea). The propofol plasma concentrations in this study varied between 0 and 7.73 (SEM 0.96) micrograms/mL. A significant correlation for the increasing propofol plasma concentration and a decrease in myocardial contractility (P = 0.0056) was demonstrated, and the Ea remained constant. This gave rise to a reduction in stroke volume (P = 0.002) and, combined with a decrease in the heart rate (P = 0.0001), led to a reduction in the cardiac output (P = 0.0001). When the propofol infusion was stopped, myocardial contractility did not recover in parallel with the decrease in plasma propofol concentration.

Breed differences in plasma calcium, phosphorus and magnesium concentrations of Merino, Dohne Merino and S.A. Mutton Merino sheep with relation to the bent-leg syndrome

Plasma calcium, phosphorus and magnesium concentrations were determined in ewes and their single and twin lambs from birth for 120 days in Merino, Dohne Merino and South African Mutton Merino sheep. Mineral concentrations as well as the plasma calcium: phosphorus ratio were compared between breeds. Throughout the experimental period, plasma calcium and phosphorus concentrations were higher in both single and twin lambs than in the ewes of all 3 breeds. No breed differences in plasma calcium concentrations were found. Animals of the S.A. Mutton Merino breed had significantly higher (P less than 0.05) plasma phosphorus concentrations than the other 2 breeds. The plasma Ca:P ratio in the Merino and Dohne Merino ram lambs was approximately 1.1:1 and in the S.A. Mutton Merino 0.9:1. This converse plasma Ca:P ratio found in both the S.A. Mutton Merino ewes and lambs is believed to result in an induced plasma ionised calcium deficiency which leads to improper calcification of bone. This is believed to be a contributing factor in the bent-leg syndrome. No difference was recorded in body mass between ram lambs suffering from the bent-leg syndrome and unaffected ram lambs. Plasma magnesium concentrations were not affected by breed or age of the animals.

Extraction of carbon 14-labeled compounds from plant tissue during processing for electron microscopy

Loss of 14C-labeled compounds from bean leaf tissue was monitored during all the stages of routine specimen preparation. No significant differences in extraction were associated with the use of acetone, ethanol, or dioxane as dehydration fluids. Fixation at low temperature increased the loss of label. Prolonged fixation in glutaraldehyde increased the loss, but fixation in osmium solutions for periods as long as 4 hr had no influence on extraction. Buffer rinses and dehydration fluids caused appreciable amounts of label to be extracted. The use of propylene oxide as transition fluid resulted in low extraction. Some embedding media caused the loss of small amounts of labeled compounds, but one of the media tested (LR-white) extracted significant amounts of label.

Measurement of human serum parathyroid hormone in disorders of calcium metabolism and during administration of certain gut hormones

A sensitive radio-immunoassay for parathyroid hormone (PTH) using the commercially available antisera AS 211/32 and AS 211/41 has been established. The lower limit of sensitivity of the assay is 0,25 ng/ml. Seventy-nine per cent of normal subjects have PTH levels in the measurable range, with a mean of 0,49 ng/ml (SD +/- 0,26 ng/ml). Only 1 of 9 patients with proven primary hyperparathyroidism had a normal serum PTH value. The mean serum PTH value in this group was 3,0 +/- 0,26 ng/ml, which differed significantly from that in the normal group (P < 0,001). The serum PTH level of 33 patients on chronic haemodialysis was uniformly raised, while in 8 patients with hypoparathyroidism PTH levels were undetectable. Patients with malignant disease presented a mixed picture, with raised, normal or undetectable PTH levels. We investigated a possible relationship between the gut hormones, gastrin, secretin and cholecystokinin-pancreozymin (CCK-PK) and PTH secretion in human volunteers. No effect was found, although the investigations were conducted over relatively short time periods.