A review of current therapeutics targeting the mitochondrial protease ClpP in diffuse midline glioma, H3 K27-altered

Diffuse midline gliomas (DMGs) are devastating pediatric brain tumors recognized as the leading cause of cancer-related death in children. DMGs are high-grade gliomas (HGGs) diagnosed along the brain's midline. Euchromatin is the hallmark feature of DMG, caused by global hypomethylation of H3K27 either through point mutations in histone H3 genes (H3K27M), or by overexpression of the enhancer of zeste homolog inhibitory protein. In a clinical trial for adults with progressive HGGs, a 22-year-old patient with a thalamic DMG, H3 K27-altered, showed a remarkable clinical and radiological response to dordaviprone (ONC201). This response in an H3 K27-altered HGG patient, coupled with the lack of response of patients harboring wildtype-H3 tumors, has increased the clinical interest in dordaviprone for the treatment of DMG. Additional reports of clinical benefit have emerged, but research defining mechanisms of action (MOA) fall behind dordaviprone's clinical use, with biomarkers of response unresolved. Here, we summarize dordaviprone's safety, interrogate its preclinical MOA identifying the mitochondrial protease "ClpP" as a biomarker of response, and discuss other ClpP agonists, expanding the arsenal of potential weapons in the fight against DMG. Finally, we discuss combination strategies including ClpP agonists, and their immunomodulatory effects suggestive of a role for the tumor microenvironment in DMG patient response.

PI3K/mTOR is a therapeutically targetable genetic dependency in diffuse intrinsic pontine glioma

Diffuse midline glioma (DMG), including tumors diagnosed in the brainstem (diffuse intrinsic pontine glioma; DIPG), are uniformly fatal brain tumors that lack effective treatment. Analysis of CRISPR/Cas9 loss-of-function gene deletion screens identified PIK3CA and MTOR as targetable molecular dependencies across patient derived models of DIPG, highlighting the therapeutic potential of the blood-brain barrier-penetrant PI3K/Akt/mTOR inhibitor, paxalisib. At the human-equivalent maximum tolerated dose, mice treated with paxalisib experienced systemic glucose feedback and increased insulin levels commensurate with patients using PI3K inhibitors. To exploit genetic dependence and overcome resistance while maintaining compliance and therapeutic benefit, we combined paxalisib with the antihyperglycemic drug metformin. Metformin restored glucose homeostasis and decreased phosphorylation of the insulin receptor in vivo, a common mechanism of PI3K-inhibitor resistance, extending survival of orthotopic models. DIPG models treated with paxalisib increased calcium-activated PKC signaling. The brain penetrant PKC inhibitor enzastaurin, in combination with paxalisib, synergistically extended the survival of multiple orthotopic patient-derived and immunocompetent syngeneic allograft models; benefits potentiated in combination with metformin and standard-of-care radiotherapy. Therapeutic adaptation was assessed using spatial transcriptomics and ATAC-Seq, identifying changes in myelination and tumor immune microenvironment crosstalk. Collectively, this study has identified what we believe to be a clinically relevant DIPG therapeutic combinational strategy.

Therapeutic HDAC inhibition in hypermutant diffuse intrinsic pontine glioma

Constitutional mismatch repair deficiency (CMMRD) is a cancer predisposition syndrome associated with the development of hypermutant pediatric high-grade glioma, and confers a poor prognosis. While therapeutic histone deacetylase (HDAC) inhibition of diffuse intrinsic pontine glioma (DIPG) has been reported; here, we use a clinically relevant biopsy-derived hypermutant DIPG model (PBT-24FH) and a CRISPR-Cas9 induced genetic model to evaluate the efficacy of HDAC inhibition against hypermutant DIPG. We screened PBT-24FH cells for sensitivity to a panel of HDAC inhibitors (HDACis) in vitro, identifying two HDACis associated with low nanomolar IC50s, quisinostat (27 nM) and romidepsin (2 nM). In vivo, quisinostat proved more efficacious, inducing near-complete tumor regression in a PBT-24FH flank model. RNA sequencing revealed significant quisinostat-driven changes in gene expression, including upregulation of neural and pro-inflammatory genes. To validate the observed potency of quisinostat in vivo against additional hypermutant DIPG models, we tested quisinostat in genetically-induced mismatch repair (MMR)-deficient DIPG flank tumors, demonstrating that loss of MMR function increases sensitivity to quisinostat in vivo. Here, we establish the preclinical efficacy of quisinostat against hypermutant DIPG, supporting further investigation of epigenetic targeting of hypermutant pediatric cancers with the potential for clinical translation. These findings support further investigation of HDAC inhibitors against pontine high-grade gliomas, beyond only those with histone mutations, as well as against other hypermutant central nervous system tumors.

ONC201 in combination with paxalisib for the treatment of H3K27-altered diffuse midline glioma

Diffuse midline gliomas (DMG), including diffuse intrinsic pontine gliomas (DIPGs), are the most lethal of childhood cancers. Palliative radiotherapy is the only established treatment, with median patient survival of 9-11 months. ONC201 is a DRD2 antagonist and ClpP agonist that has shown preclinical and emerging clinical efficacy in DMG. However, further work is needed to identify the mechanisms of response of DIPGs to ONC201 treatment and to determine whether recurring genomic features influence response. Using a systems-biological approach, we showed that ONC201 elicits potent agonism of the mitochondrial protease ClpP to drive proteolysis of electron transport chain and tricarboxylic acid cycle proteins. DIPGs harboring PIK3CA-mutations showed increased sensitivity to ONC201, while those harboring TP53-mutations were more resistant. Metabolic adaptation and reduced sensitivity to ONC201 was promoted by redox-activated PI3K/Akt signaling, which could be counteracted using the brain penetrant PI3K/Akt inhibitor, paxalisib. Together, these discoveries coupled with the powerful anti-DIPG/DMG pharmacokinetic and pharmacodynamic properties of ONC201 and paxalisib have provided the rationale for the ongoing DIPG/DMG phase II combination clinical trial NCT05009992.

Blockade of ROS production inhibits oncogenic signaling in acute myeloid leukemia and amplifies response to precision therapies

Mutations in the type III receptor tyrosine kinase FLT3 are frequent in patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. AML is characterized by the overproduction of reactive oxygen species (ROS), which can induce cysteine oxidation in redox-sensitive signaling proteins. Here, we sought to characterize the specific pathways affected by ROS in AML by assessing oncogenic signaling in primary AML samples. The oxidation or phosphorylation of signaling proteins that mediate growth and proliferation was increased in samples from patient subtypes with FLT3 mutations. These samples also showed increases in the oxidation of proteins in the ROS-producing Rac/NADPH oxidase-2 (NOX2) complex. Inhibition of NOX2 increased the apoptosis of FLT3-mutant AML cells in response to FLT3 inhibitors. NOX2 inhibition also reduced the phosphorylation and cysteine oxidation of FLT3 in patient-derived xenograft mouse models, suggesting that decreased oxidative stress reduces the oncogenic signaling of FLT3. In mice grafted with FLT3 mutant AML cells, treatment with a NOX2 inhibitor reduced the number of circulating cancer cells, and combining FLT3 and NOX2 inhibitors increased survival to a greater extent than either treatment alone. Together, these data raise the possibility that combining NOX2 and FLT3 inhibitors could improve the treatment of FLT3 mutant AML.

Phospho-heavy-labeled-spiketide FAIMS stepped-CV DDA (pHASED) provides real-time phosphoproteomics data to aid in cancer drug selection

Global high-throughput phosphoproteomic profiling is increasingly being applied to cancer specimens to identify the oncogenic signaling cascades responsible for promoting disease initiation and disease progression; pathways that are often invisible to genomics analysis. Hence, phosphoproteomic profiling has enormous potential to inform and improve individualized anti-cancer treatment strategies. However, to achieve the adequate phosphoproteomic depth and coverage necessary to identify the activated, and hence, targetable kinases responsible for driving oncogenic signaling pathways, affinity phosphopeptide enrichment techniques are required and often coupled with offline high-pressure liquid chromatographic (HPLC) separation prior to nanoflow liquid chromatography-tandem mass spectrometry (nLC-MS/MS). These complex and time-consuming procedures, limit the utility of phosphoproteomics for the analysis of individual cancer patient specimens in real-time, and restrict phosphoproteomics to specialized laboratories often outside of the clinical setting. To address these limitations, here we have optimized a new protocol, phospho-heavy-labeled-spiketide FAIMS Stepped-CV DDA (pHASED), that employs online phosphoproteome deconvolution using high-field asymmetric waveform ion mobility spectrometry (FAIMS) and internal phosphopeptide standards to provide accurate label-free quantitation (LFQ) data in real-time. Compared with traditional single-shot LFQ phosphoproteomics workflows, pHASED provided increased phosphoproteomic depth and coverage (phosphopeptides = 4617 pHASED, 2789 LFQ), whilst eliminating the variability associated with offline prefractionation. pHASED was optimized using tyrosine kinase inhibitor (sorafenib) resistant isogenic FLT3-mutant acute myeloid leukemia (AML) cell line models. Bioinformatic analysis identified differential activation of the serine/threonine protein kinase ataxia-telangiectasia mutated (ATM) pathway, responsible for sensing and repairing DNA damage in sorafenib-resistant AML cell line models, thereby uncovering a potential therapeutic opportunity. Herein, we have optimized a rapid, reproducible, and flexible protocol for the characterization of complex cancer phosphoproteomes in real-time, a step towards the implementation of phosphoproteomics in the clinic to aid in the selection of anti-cancer therapies for patients.

B-cell Lymphoma 6 (BCL6): From Master Regulator of Humoral Immunity to Oncogenic Driver in Pediatric Cancers

B-cell lymphoma 6 (BCL6) is a protooncogene in adult and pediatric cancers, first identified in diffuse large B-cell lymphoma (DLBCL) where it acts as a repressor of the tumor suppressor TP53, conferring survival, protection, and maintenance of lymphoma cells. BCL6 expression in normal B cells is fundamental in the regulation of humoral immunity, via initiation and maintenance of the germinal centers (GC). Its role in B cells during the production of high affinity immunoglobins (that recognize and bind specific antigens) is believed to underpin its function as an oncogene. BCL6 is known to drive the self-renewal capacity of leukemia-initiating cells (LIC), with high BCL6 expression in acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and glioblastoma (GBM) associated with disease progression and treatment resistance. The mechanisms underpinning BCL6-driven therapy resistance are yet to be uncovered; however, high activity is considered to confer poor prognosis in the clinical setting. BCL6's key binding partner, BCL6 corepressor (BCOR), is frequently mutated in pediatric cancers and appears to act in concert with BCL6. Using publicly available data, here we show that BCL6 is ubiquitously overexpressed in pediatric brain tumors, inversely to BCOR, highlighting the potential for targeting BCL6 in these often lethal and untreatable cancers. In this review, we summarize what is known of BCL6 (role, effect, mechanisms) in pediatric cancers, highlighting the two sides of BCL6 function, humoral immunity, and tumorigenesis, as well as to review BCL6 inhibitors and highlight areas of opportunity to improve the outcomes of patients with pediatric cancer.

DIPG-07. Preclinical and case study results underpinning the phase II clinical trial testing the combination of ONC201 and paxalisib for the treatment of patients with diffuse midline glioma (NCT05009992)

Diffuse midline gliomas (DMG), including those of the brainstem (diffuse intrinsic pontine glioma - DIPG), are pediatric CNS tumors recognized as the most lethal of all children’s cancers. Palliative radiotherapy is the only approved treatment, with survival just 9-11–months post-diagnosis. ONC201 shows preclinical and emerging clinical efficacy in early-stage clinical trials, extending survival of DIPG patients by ~9-11–months compared to historic controls. However, patients invariably develop resistance, with some patients completely refractory to treatment. Using a multi-omics approach, including pharmacology, proteomics, genomics, epigenetics, in vitro and in vivo modeling, across ten international laboratories, we have uncovered the inherent mechanisms of resistance to ONC201. We find ONC201 elicits antagonism of the Dopamine receptor D2 (DRD2), whilst also causing mitochondrial degradation through potent agonism of the Mitochondrial protease CLPP, that drives proteolysis of the electron transport chain (ETC) protein Succinate dehydrogenase A (SDHA) and degradation of critical mitochondrial tricarboxylic acid (TCA) cycle regulator Isocitrate dehydrogenase 3B (IDH3B). Loss mitochondrial respiration increased hypoxia and reduced α-ketoglutarate, inhibiting lysine demethylation, increasing methylation of H3K4me3 and H3K27me3, thus altering the epigenome of primary DIPG cells. Loss of SDHA caused oxidation of succinate forming superoxide driving redox regulated PI3K/AKT signaling, counteracted using the PI3K/AKT inhibitor paxalisib. The combination of ONC201 and paxalisib synergically extended survival of two aggressive DIPG PDX models (SU-SIPG-VI vehicle=73 vs. combination=100-days, p=0.0027; SF8626 vehicle=36 vs. combination=43-days, p=0.0002). Compassionate access to this combination (n=2 patients; immediately post-RT and following re-RT) resulted in reductions in tumor volume and complete resolution of disease symptoms, extending overall survival (e.g., diagnosis patient MR axial scan=1554 mm2 , following eight months on the combination, current tumor volume=464 mm2 (<70%), patient remains on treatment). Our findings harness the powerful anti-DMG/DIPG pharmacokinetic/dynamic properties of ONC201 and paxalisib, a combination that is currently in clinical trials (NCT05009992).

Preclinical and clinical evaluation of German-sourced ONC201 for the treatment of H3K27M-mutant diffuse intrinsic pontine glioma

Background

Diffuse intrinsic pontine glioma (DIPG) is a fatal childhood brainstem tumor for which radiation is the only treatment. Case studies report a clinical response to ONC201 for patients with H3K27M-mutant gliomas. Oncoceutics (ONC201) is only available in the United States and Japan; however, in Germany, DIPG patients can be prescribed and dispensed a locally produced compound—ONC201 German-sourced ONC201 (GsONC201). Pediatric oncologists face the dilemma of supporting the administration of GsONC201 as conjecture surrounds its authenticity. Therefore, we compared GsONC201 to original ONC201 manufactured by Oncoceutics Inc.

Methods

Authenticity of GsONC201 was determined by high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy. Biological activity was shown via assessment of on-target effects, in vitro growth, proliferation, and apoptosis analysis. Patient-derived xenograft mouse models were used to assess plasma and brain tissue pharmacokinetics, pharmacodynamics, and overall survival (OS). The clinical experience of 28 H3K27M+ mutant DIPG patients who received GsONC201 (2017–2020) was analyzed.

Results

GsONC201 harbored the authentic structure, however, was formulated as a free base rather than the dihydrochloride salt used in clinical trials. GsONC201 in vitro and in vivo efficacy and drug bioavailability studies showed no difference compared to Oncoceutics ONC201. Patients treated with GsONC201 (n = 28) showed a median OS of 18 months (P = .0007). GsONC201 patients who underwent reirradiation showed a median OS of 22 months compared to 12 months for GsONC201 patients who did not (P = .012).

Conclusions

This study confirms the biological activity of GsONC201 and documents the OS of patients who received the drug; however, GsONC201 was never used as a monotherapy.

DIPG-29. PHOSPHATIDYLINOSITOL-4,5-BISPHOSPHATE 3-KINASE (PI3K) INHIBITION DRIVES PROTEIN KINASE C ACTIVATION (PKC) IN DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)

Recurring somatic mutations and gene amplifications to members of the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) signaling axis are overarching contributors to the aggressive growth and survival of diffuse intrinsic pontine gliomas (DIPG). However, targeting PI3K has thus far failed to improve outcomes for patients in the clinic. To identify the mechanisms underpinning PI3K/AKT/mTOR treatment failure in DIPG, we have employed high-resolution quantitative phosphoproteomic profiling in patient-derived DIPG cell lines harboring H3K27M and PI3K mutations, +/- the blood-brain barrier permeable PI3K inhibitor, paxalisib (previously “GDC-0084”, currently in Phase I trials - NCT03696355) and rapamycin. Paxalisib was significantly more potent than rapamycin at inducing PI3K/AKT/mTOR inhibition, however, both simultaneously activated protein kinase C signaling (pT500PKCβ +8.2 and +4.5 fold, respectively). PKC lies directly upstream of myristoylated alanine-rich C-kinase substrate (MARCKs), which was phosphorylated at Ser170 by +9.4 and +4.7 fold, respectively; promoting actin cytoskeletal remodeling and cellular migration. Indeed, activation of PKC signaling using phorbol 12-myristate 13-acetate (PMA), increased DIPG cell growth and migration by >3 fold. Targeting PKC using midostaurin (FDA-approved for acute myeloid leukemia), and enzastaurin (blood-brain barrier penetrant inhibitor of PKCβ), in combination with paxalisib was highly synergistic (CI=<0.9), reducing proliferation and driving apoptosis. Mechanistically, compensatory activation of PKC signaling following PI3K inhibition was regulated by the accumulation of Ca+2 ions, as chelation using BAPTA-AM significantly reduced PKC activity following PI3K inhibition. These data highlight the power of phosphoproteomic profiling for the rational design of drug combination strategies, which need to be tested in vivo prior to clinical trials for DIPG.

DIPG-32. AKT SIGNALING DRIVES RESISTANCE TO ONC201 IN DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG)

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive, childhood brainstem cancer with a median overall survival of 10 months post diagnosis. Remarkably, 80–90% of patients harbor recurring point mutation in histone H3, which induces a lysine for methionine substitution at amino acid 27 (H3K27M) in either H3.1 (HIST1H3B ~25%) or H3.3 (H3F3A ~65%) variants. Using the blood-brain barrier (BBB) permeable DRD2 antagonist, ONC201 (in clinical trials for DIPG and H3K27M-mutant gliomas – NCT03416530), we hypothesized that DRD2 antagonism would induce TRAIL expression via indirect inhibition of AKT and ERK signaling, to drive apoptosis in both H3.1K27M and H3.3K27M patient-derived DIPG cell lines alike. For the first time, we reveal that ONC201 shows efficacy in 100% of WT-H3 and H3.1K27M mutant DIPG cell lines (n=5), compared to 50% of H3.3K27M mutant DIPGs (n=6). Investigations to identify the mechanisms of resistance to ONC201, revealed that cell lines with decreased sensitivity upregulated the PI3K/AKT/MTOR signaling axis to drive phosphorylation of AKT and increase metabolic activity. Combined administration of ONC201 and the BBB-permeable PI3K/AKT inhibitor, paxalisib (previously GDC-0084, in clinical trials for newly diagnosed DIPG – NCT03696355), showed synergistic cytotoxicity, reduced PI3K/AKT signaling and metabolic reprogramming to drive apoptosis in all DIPG cell lines tested. This combination was used to treat a 3-year-old DIPG patient, commencing 14 weeks post disease progression, completing 40 weeks of therapy prior to her passing, December 2019. These studies highlight the potential of combined administration of two safe, BBB penetrant, oral targeted therapies and supports testing under clinical trial conditions.

Synthesis, SAR and pharmacology of CP-293,019: a potent, selective dopamine D4 receptor antagonist

A series of novel, potent and selective pyrido[1,2-a]pyrazine dopamine D4 receptor antagonists are reported including CP-293,019 (D4 Ki = 3.4 nM, D2 Ki > 3,310 nM), which also inhibits apomorphine-induced hyperlocomotion in rats after oral dosing.

Discovery of CP-96,345 and its characterization in disease models involving substance P

Studies with CP-96,345, a potent, selective, orally active, nonpeptide NK1 receptor antagonist, have provided considerable insight into SP pharmacology. Rather than being a primary neurotransmitter, SP prolongs the nociception produced by other neurotransmitters. By controlling endothelial permeability, SP plays a major role in inflammation and inflammatory aspects of asthma, possibly by regulating the access of neutrophils to an inflammatory site. These results indicate potential therapeutic applications for SP antagonists in the treatment of chronic pain, inflammation, and inflammatory aspects of asthma, and signal a new era in the clinical management of these important diseases.

The proper use and benefits of veterinary antimicrobial agents in practice in cattle

A rational basis for the therapeutic and prophylactic use of antimicrobials is discussed. Different approaches are needed to deal with the individual animal, group or herd disease problem. Improved antibiotic preparations are needed to enhance the efficacy of treatment and minimise suffering and lost production.

The discovery of (2S,3S)-cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)methyl]-1- azabicyclo[2.2.2]-octan-3-amine as a novel, nonpeptide substance P antagonisst

We describe the structure-activity relationship development of a series of quinuclidines which culminated in the first potent, selective, nonpeptide substance P (SP) antagonist, (2S,3S)-cis-2-(diphenylmethyl)-N-[(2-methoxy-phenyl)methyl]-1- azabicyclo[2.2.2]octan-3-amine, 3 (CP-96,345). Compound 3 is a potent displacer of [3H]SP binding in human IM-9 cells and blocks SP-induced and capsaicin-induced plasma extravasation, as well as SP-induced salivation in the rat in vivo. This compound may both help to further our understanding of the interactions of small molecules with peptide receptors and serve to evaluate the therapeutic potential of a SP antagonist.

Intracavitary right heart cooling during coronary bypass surgery. A prospective randomized trial

Augmented right heart cooling (RHC) with bicaval cannulation, pulmonary artery venting, and intracavitary cooling has been advocated for prevention of right ventricular failure and supraventricular tachyarrhythmias after open heart surgery. To evaluate RHC, 78 patients undergoing coronary bypass surgery were prospectively randomized to receive added RHC (n = 38) or standard protection with single atrial cannulation (SC) (n = 40). RHC and SC patients were similar regarding right coronary artery occlusion (n = 10 and 12, respectively), number of grafts performed (3.7 +/- 1.0 and 3.4 +/- 0.9), and cross-clamp time per graft (10.2 +/- 1.8 and 9.8 +/- 2.3 minutes). RHC led to significantly lower right atrial (11.6 degrees +/- 1.0 degree vs. 19.5 degrees +/- 3.3 degrees C) and right ventricular (7.2 degrees +/- 1.9 degrees vs. 12.2 degrees +/- 1.9 degrees C) temperatures. There was no detectable deterioration in right heart function or left heart function in either group after cardiopulmonary bypass. Bypass time was longer in RHC patients (86.7 +/- 17.9 vs. 76.0 +/- 18.2 minutes, p less than 0.05). Technical problems related to multiple cannulation occurred in four RHC patients. After cross-clamp removal, creatine kinase-MB levels were significantly higher with RHC at 2 hours (14.2 +/- 7.6 vs. 6.4 +/- 4.6 IU/l, p less than 0.001), 12 hours (19.1 +/- 19.5 vs. 8.6 +/- 10.3 IU/l, p less than 0.005), and 24 hours (14.1 +/- 19.6 vs. 7.1 +/- 9.2 IU/l, p less than 0.05). Mortality and morbidity were similar in the two groups. In particular, supraventricular tachyarrythmias occurred in 11 (28.9%) RHC and 10 (25%) SC patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Trends in invasive treatment of single-vessel and double-vessel coronary disease

We examined our practice of invasive therapy for one- and two-vessel coronary disease to assess the impact of the randomized trials of coronary surgery and the current use of angioplasty. We first reviewed our results with coronary artery bypass graft in equivalent patients in the Coronary Artery Surgery Study with one- and two-vessel disease between 1976 and 1981. Among 1376 patients, hospital mortality was 0.07%, and 5-year survival was 95.2% +/- 0.8%. To define trends in invasive therapy, which have since occurred, we compared 100 patients with one- and two-vessel disease in each of three groups: 1979 coronary artery bypass graft, 1984 coronary artery bypass graft, and 1984 percutaneous transluminal coronary angioplasty. Preoperative characteristics in the average 1979 and 1984 patients were similar; however, in 1984, patients who had a coronary artery bypass graft were older than patients who had percutaneous transluminal coronary angioplasty (61.5 versus 56.7 years, p less than 0.01), they required more heart medications (2.1 versus 1.5, p less than 0.01), had more previous infarctions (0.8 versus 0.5, p less than 0.01), and more patients had an ejection fraction of less than 50% (34% versus 7%, p less than 0.01). Patients who had angioplasty had a shorter postoperative stay (median number of days 7, 7, 2, p less than 0.01). Freedom from major complications was similar among the groups (91%, 87%, 85%). Unstable symptoms were the most frequent indication for invasive therapy (approximately 80%), whereas long-term symptoms, those considered in the randomized trials, occurred in relatively few patients. The number of patients without at least one definite indication for invasive therapy was 13%, 3%, and 11%, p less than 0.05, suggesting that the indications for the 1984 coronary artery bypass graft group have become more restrictive since the 1979 coronary artery bypass graft group. Indications for the 1984 percutaneous transluminal coronary angioplasty group remained less restrictive, being similar to those for the 1979 coronary artery bypass graft group. A continuing trend toward the use of percutaneous transluminal coronary angioplasty was evident, as 56% of the 1979 coronary artery bypass graft group of patients and 32% of the 1984 coronary bypass group of patients would be offered percutaneous transluminal coronary angioplasty rather than coronary artery bypass graft on the basis of 1986 percutaneous transluminal coronary angioplasty criteria. The p values were obtained with analysis of variance or chi 2 test.

Gene networks in development

A model is presented for the formation of temporal and spatial patterns of cell types during the development of organisms. It is demonstrated that very simple random networks of interactions among genes that affect expression may lead to the autonomous development of patterns of cell types. It is required that the networks contain active feedback loops and that there is limited communication among cells. The only elements of the model, gene interactions, are specified by the DNA nucleotide sequences of the genes. Therefore, the model readily explains how the control of development is specified by the organism's DNA. In the context of this model, the formation of positional information and its interpretation becomes a single process.

Within herd comparison of teat dipping and dry cow therapy with only selective dry cow therapy in six herds

A within herd comparison of teat dipping and dry cow therapy (full treatment) with only selective dry cow therapy (partial treatment) was carried out in six commercial dairy herds for a two year period. In four herds, the incidence of clinical mastitis was 2 to 12 per cent higher in the partial treatment group. In another herd, in which the pattern of clinical mastitis isolates was unusual in that minor pathogens were isolated from 30 per cent of mastitis cases, the incidence was 43 per cent higher in the partial treatment group. In the remaining herd the incidence was 10 percent higher in the full treatment group. Streptococcus uberis mastitis was more common in the partial treatment groups of five herds; coliform mastitis was more common in the full treatment groups of two herds and similar in both groups in the other herds. High rates of coliform mastitis were associated with poor herd environmental conditions but this was not true for Strep uberis mastitis. Rates of staphylococcus aureus and Strep dysgalactiae mastitis were low in all herds. The level of major pathogen infection in cows completing the trial in all herds increased in the partial treatment group from 5 per cent of quarters at the start to 12 per cent at the finish of the trial. In the full treatment group, however, there was only a small increase in this level. In contrast, levels of Corynebacterium bovis infection increased by 17 per cent in both treatment groups. Continued use of teat dipping and dry cow therapy was associated with a higher rate of coliform mastitis in two of the three herds where there were poor standards of hygiene and husbandry.

Susceptibility of the bovine udder to bacterial infection in the dry period

The teats of 18 cows were externally exposed to infection with mastitis organisms by dipping them daily for 1 or 2 weeks in a mixed suspension of Streptococcus dysgalactiae and Str. uberis at the start, the middle or the end of the dry period. The teat sinuses of quarters which remained uninfected after external exposure at the beginning or the middle of the dry period were then infused with the same strains of streptococci. Of the 9 quarters infected following external exposure 8 occurred in animals exposed at the start and one in the middle of the dry period. Thirty-six new infections occurred after infusion of bacteria into the teat sinuses of 38 quarters. In a further trial with 10 cows, Staphylococcus aureus and Str. zooepidemicus were inoculated into the distal 3 mm of the streak canals of 5 cows immediately after drying-off and into those of 5 cows which had been dry for 28 weeks. Animals were slaughtered 48 h later and infection determined by teat puncture. Five infections occurred in cows which were at the start of the dry period and only one in the cows dry for 28 weeks. It is suggested that these differences in the rates of new infection between the early dry period and a very extended dry period are due to differences in the ease with which bacteria can penetrate the teat canal. At the later stage bacterial growth through the teat canal appeared to be inhibited.

Pesticide Residues in Commercial Animal Feeds

One hundred and one commercial feeds, of which 87 were dairy feeds or supplements, were analyzed for chlorinated organic pesticide residues by gas chromatography utilizing 5% SE-30 for the stationary phase and electron capture detection. A computation scheme for determining γ-BHC, aldrin, dieldrin, endrin, DDD, DDT, methoxychlor, heptachlor, heptachlor epoxide, chlordane, and toxaphene in combination with each other was developed, and values were tabulated for each in each feed. Contaminations ranged from low tens to hundreds (ppb). Most of the feeds contained residue amounts below those which would be expected to produce detectable residues in milk. Higher contamination levels were tentatively correlated with specific feed ingredients, as well as with protein and crude fiber content. Higher contaminations were observed with higher fiber content, lower feed protein value, and when grain screenings, rice bran, or rice mill by-product were ingredients. Much lower contaminations were associated with ground milo, wheat bran and middlings, ground and crimped oats, linseed oil meal, and various corn products.