Bending the Rules: Amplifying PD-L1 Immunoregulatory Function Through Flexible Polyethylene Glycol Synthetic Linkers

Immune checkpoint signaling, such as programmed cell death protein-1 (PD-1), is a key target for immunotherapy due to its role in dampening immune responses. PD-1 signaling in T cells is regulated by complex physicochemical and mechanical cues. However, how these mechanical forces are integrated with biochemical responses remains poorly understood. Our previous work demonstrated that the use of an immobilizing polyethylene glycol (PEG) linker on synthetic microgels for the presentation of a chimeric form of PD-L1, SA-PD-L1, lead to local regulatory responses capable of abrogating allograft rejection in a model of cell-based transplantation. We herein provide evidence that enhanced immune regulating function can be obtained when presentation of SA-PD-L1 is achieved through a longer more flexible PEG chain. Presentation of SA-PD-L1 through a linker of high molecular weight, and thus longer length (10 kDa, 60 nm in length), led to enhance conversion of naive T cells into T regulatory cells (Tregs) in vitro. In addition, using a subcutaneous implant model and protein tethered through three different linker sizes (6, 30, and 60 nm) to the surface of PEG hydrogels, we demonstrated that longer linkers promoted PD-1 immunomodulatory role in vivo through three main functions: (1) augmenting immune cell recruitment at the transplant site; (2) promoting the accumulation of naive Tregs expressing migratory markers; and (3) dampening CD8+ cytolytic molecule production while augmenting expression of exhaustion phenotypes locally. Notably, accumulation of Treg cells at the implant site persisted for over 30 days postimplantation, an effect not observed when protein was presented with the shorter version of the linkers (6 and 30 nm). Collectively, these studies reveal a facile approach by which PD-L1 function can be modulated through external tuning of synthetic presenting linkers. Impact statement Recently, there has been a growing interest in immune checkpoint molecules as potential targets for tolerance induction, including programmed cell death protein-1 (PD-1). However, how the mechanics of ligand binding to PD-1 receptor affect downstream activation signaling pathways remains unresolved. By taking advantage of the effect of polyethylene glycol chain length on molecule kinetics in an aqueous solution, we herein show that PD-L1 function can be amplified by adjusting the length of the grafting linker. Our results uncover a potential facile mechanism that can be exploited to advance the role of immune checkpoint ligands, in particular PD-L1, in tolerance induction for immunosuppression-free cell-based therapies.

Delayed graft rejection in autoimmune islet transplantation via biomaterial immunotherapy

The induction of operational immune tolerance is a major goal in beta-cell replacement strategies for the treatment of type 1 diabetes. Our group previously reported long-term efficacy via biomaterial-mediated programmed death ligand 1 (PD-L1) immunotherapy in islet allografts in nonautoimmune models. In this study, we evaluated autoimmune recurrence and allograft rejection during islet transplantation in spontaneous nonobese diabetic (NOD) mice. Graft survival and metabolic function were significantly prolonged over 60 days in recipients of syngeneic islets receiving the biomaterial-delivered immunotherapy, but not in control animals. The biomaterial-mediated PD-L1 immunotherapy resulted in delayed allograft rejection in diabetic NOD mice compared with controls. Discrimination between responders and nonresponders was attributed to the enriched presence of CD206+ program death 1+ macrophages and exhausted signatures in the cytotoxic T cell compartment in the local graft microenvironment. Notably, draining lymph nodes had similar remodeling in innate and adaptive immune cell populations. This work establishes that our biomaterial platform for PD-L1 delivery can modulate immune responses to transplanted islets in diabetic NOD mice and, thus, can provide a platform for the development of immunologic strategies to curb the allo- and autoimmune processes in beta-cell transplant recipients.

Assessment of Local and Regional Control in Atypical (WHO Grade 2) Meningiomas Receiving Fractioned Stereotactic Radiotherapy

PURPOSE/OBJECTIVE(S)

The optimal delivery of postoperative radiotherapy to WHO grade 2 or atypical meningiomas (AM) is controversial. The historical standard of care has been high dose fractionated radiation to the resection bed and a 2 cm CTV as in RTOG 0539. Single fraction radiosurgery offers a more conformal alternative with demonstrated local control for smaller AM in less sensitive areas. Though less studied, fractionated stereotactic radiosurgery (FSRT) promises safer treatment of larger AM in more sensitive locations while minimizing the treated volume. This single institution retrospective review examines the hypothesis that local and marginal failure patterns in AM treated with five fraction FSRT remain unacceptably high.

MATERIALS/METHODS

Thirty-nine patients received 27.5 - 30 Gy in 5 fractions to their AM from 2009 to 2022 with grading based on the WHO criteria active at the time of treatment. All treatments were frameless VMAT deliveries with no PTV margin. Histological diagnosis of AM, gross disease at time of FSRT, five fraction FSRT, and lack of prior local radiation were required for inclusion. Single fraction treatments were excluded. Local recurrence was defined similar to RECIST criteria as an increase of 20% in the greatest cross-sectional diameter on MRI (or CT if MRI contraindicated) with at least one voxel touching the prescription volume. To examine the role of CTV margin, marginal recurrence was defined as any new lesion outside of the prescription volume but within 2 cm of the resection cavity. High grade toxicity per CTCAE v5 was an irreversible grade 3 or any grade 4 toxicity. Resection for radionecrosis was considered a local failure if any viable tumor was seen on pathology.

RESULTS

Median follow up was 32.5 months (range 3.2-147.5 months). The number of AM treated post STR, post GTR recurrence, and definitively were 26, 16, and 5 respectively. 3-year local tumor control was estimated to be 84%. As expected, larger tumors were more likely to fail locally (p >.001). Two (5%) patients experienced high grade toxicity - both symptomatic radionecrosis requiring resection. Three-year marginal control was estimated to be 92.3%. Of the 5 tumors treated to the entire resection cavity, none experienced a marginal failure. Interestingly, recurrent tumors s/p GTR were more likely to recur marginally than tumors treated after STR (p = .009). Only 1 (4%) tumor treated after STR failed marginally while 4 (33%) tumors treated after GTR recurrence failed.

CONCLUSION

The rate of high-grade toxicity in AM receiving FSRT was low. Local control appeared comparable to historical rates which may suggest the need for dose escalation with longer term follow-up. Recurrent tumors appear more prone to marginal failures, however more work is needed to determine which patients may benefit from additional CTV margin and more prolonged fractionated dose schedules. Improved targeting with newer imaging studies (e.g., DOTATATE PET) should be examined to determine if more accurate targeting will improve outcomes.

Enteroendocrine Cells Protect the Stem Cell Niche by Regulating Crypt Metabolism in Response to Nutrients

BACKGROUND & AIMS

The intestinal stem cell niche is exquisitely sensitive to changes in diet, with high-fat diet, caloric restriction, and fasting resulting in altered crypt metabolism and intestinal stem cell function. Unlike cells on the villus, cells in the crypt are not immediately exposed to the dynamically changing contents of the lumen. We hypothesized that enteroendocrine cells (EECs), which sense environmental cues and in response release hormones and metabolites, are essential for relaying the luminal and nutritional status of the animal to cells deep in the crypt.

METHODS

We used the tamoxifen-inducible VillinCreERT2 mouse model to deplete EECs (Neurog3fl/fl) from adult intestinal epithelium and we generated human intestinal organoids from wild-type and NEUROGENIN 3 (NEUROG3)-null human pluripotent stem cells. We used indirect calorimetry, 1H-Nuclear Magnetic Resonance (NMR) metabolomics, mitochondrial live imaging, and the Seahorse bioanalyzer (Agilent Technologies) to assess metabolism. Intestinal stem cell activity was measured by proliferation and enteroid-forming capacity. Transcriptional changes were assessed using 10x Genomics single-cell sequencing.

RESULTS

Loss of EECs resulted in increased energy expenditure in mice, an abundance of active mitochondria, and a shift of crypt metabolism to fatty acid oxidation. Crypts from mouse and human intestinal organoids lacking EECs displayed increased intestinal stem cell activity and failed to activate phosphorylation of downstream target S6 kinase ribosomal protein, a marker for activity of the master metabolic regulator mammalian target of rapamycin (mTOR). These phenotypes were similar to those observed when control mice were deprived of nutrients.

CONCLUSIONS

EECs are essential regulators of crypt metabolism. Depletion of EECs recapitulated a fasting metabolic phenotype despite normal levels of ingested nutrients. These data suggest that EECs are required to relay nutritional information to the stem cell niche and are essential regulators of intestinal metabolism.

Adaptive behaviour, executive function and employment in adults with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) demonstrate difficulties with aspects of executive function (EF) and adaptive behaviour across the lifespan. There is a current lack of information regarding how these difficulties relate to employment outcomes in adulthood. This study evaluated the adaptive behaviour and EF profiles of individuals with DS during early adulthood and the association between these areas of functioning and employment status.

METHODS

Parents or caregivers of primarily young adults with DS (n = 31; mean chronological age = 25.9 years; SD = 5.92) completed the Vineland Adaptive Behavior Scales - Second Edition the Behavior Rating Inventory of Executive Function - Adult version and a demographic questionnaire that requested information regarding adult employment status.

RESULTS

Findings indicated a distinct pattern of relative strengths and challenges in adaptive behaviour and EF. In addition, the EF sub-domain of working memory was a significant predictor of employment status.

CONCLUSIONS

Specific aspects of the DS cognitive profile may have an important influence on employment status in primarily young adults with DS. Implications for interventions are discussed.

Mortality among veterans with type 2 diabetes initiating metformin, sulfonylurea or rosiglitazone monotherapy

AIMS/HYPOTHESES

Despite oral hypoglycaemic medications being the most commonly used pharmacological treatments for type 2 diabetes, research is limited on their comparative safety, particularly their effects on overall mortality. We compared mortality risk with monotherapy initiation of four oral hypoglycaemic medications in a nationwide cohort of US veterans with type 2 diabetes.

METHODS

We identified new users of oral hypoglycaemic medication monotherapy between 2004 and 2009 who received care for at least 1 year from the Veterans Health Administration.Patients were followed until initial monotherapy discontinuation,addition of another diabetes pharmacotherapy, death or end of follow-up. Mortality HRs were estimated using Cox regression adjusted for potential confounding factors.

RESULTS

Among new users of metformin, sulfonylureas and rosiglitazone (185,360 men, 7,812 women), 4,256 (2.2%) died during follow-up. Average duration of medication use ranged from 1.4 to 1.7 years. Significantly higher mortality risk was seen for glibenclamide (known as glyburide in the USA and Canada) (HR 1.38, 95% CI 1.27, 1.50) or glipizide (HR 1.55,95% CI 1.43, 1.67) compared with metformin monotherapy,and for glipizide compared with rosiglitazone (HR 1.27, 95%CI 1.01, 1.59) or glibenclamide monotherapy (HR 1.12, 95%CI 1.02, 1.23). A significant sex–rosiglitazone interaction was seen (p=0.034) compared with metformin monotherapy, with women having a higher HR (HR 4.36, 95% CI 1.34, 14.20)than men (HR 1.19, 95% CI 0.95, 1.49).

CONCLUSIONS/INTERPRETATIONS

Significantly higher mortality was associated with glibenclamide, glipizide and rosiglitazone use compared with metformin, and with glipizide use compared with rosiglitazone or glibenclamide. The potential for residual confounding by indication should be considered in interpreting these results.

SU-E-T-158: Neutron Damage of Power Electronics Used during Image Guidance in Proton Therapy

PURPOSE

A series of measurements were performed in a clinical proton therapy beam to assess the sensitivity of silicon-based electronics in commercial x-ray generators to single event burnout from the secondary neutron background in proton therapy treatments.

METHODS

Failure rates were nondestructively measured in various metal oxide semiconductor field-effect transistors (MOSFETs) as a function of applied voltage using a dedicated test circuit board. Neutrons were produced by 230 MeV protons stopping in a brass beam target and high beam current was used to accelerate testing. Neutron fluences were measured by activation analysis of carbon and aluminum in both the test setup and in situ at the generator. Failure rates were determined by scaling results based on beam monitor output to the relevant neutron fluence rate.

RESULTS

Current pulses from the test board clearly indicated the onset of single event burnout without destroying the MOSFET. The neutron fluence measured on the test board was 4.3 ± 0.8×106 n cm-2 MU-1 and this is consistent with previous measurements. The MOSFET failure rate decreased rapidly with a reduction in the applied voltage and is 20-30 times lower in higher-rated components at the same voltage. Under nominal operating conditions the estimated failure rate is tens of failures per year for a generator 6m from the treatment position.

CONCLUSION

The sensitivity of x-ray generator power electronics to neutron-induced single-event burnout is significant and can affect the implementation of image-guided techniques for proton therapy. Strategies and system designs to mitigate this phenomenon are being investigated to help enable x-ray generators withstand the proton therapy environment. This research was supported by the NIH/NCI under grant number 6-PO1 CA 21239.

IRT-Sofia BNCT beam tube optimization study

An optimization study of IRT-Sofia BNCT beam tube is presented. In the study we used the MIT/FCB experience. The enlarging of filter/moderator cross section dimensions and the decreasing of collimator length within the limits of the IRT-Sofia reactor design were analyzed. The influence of beam and reactor core axes non-coincidence on the beam properties was also evaluated. The irradiation resistance of polytetrafluoroethylene (Teflon(®)) was also evaluated. The results provide information for making decisions on the IRT-Sofia BNCT beam construction.

Survival and neurodevelopmental morbidity at 1 year of age following extremely preterm delivery over a 20-year period: a single centre cohort study

AIM

To assess survival and neurodevelopmental outcome of extremely preterm infants over a 20-year period at a single tertiary neonatal centre.

METHODS

All infants between 22 and 25(+6) weeks of gestation admitted to a single UK neonatal centre between 1981 and 2000 were enrolled prospectively. Infants in the same gestational age range who were born alive at the hospital but not admitted to the neonatal unit were also identified over the period 1991-2000. All surviving infants received neurological and developmental assessment at a corrected age of 1 year.

RESULTS

There was a progressive increase in survival at all gestational ages over the 20-year period. Overall survival rose from 32% to 71% as a proportion of all admissions. The proportion of survivors with adverse neurodevelopmental outcome at 1 year of age showed no consistent change over the same period.

CONCLUSION

In this single centre cohort study, marked improvements in survival over a 20-year period were not accompanied by a significant increase in neurodevelopmental morbidity.

Effects of age and liveweight of dairy heifers at first calving on multiple lactation production

This paper reports on both the individual and combined effects of age and liveweight at first calving (AFC and LWFC, respectively) for Australian Holstein–Friesian heifers on multiple lactation production. One hundred and thirty-five heifers were allocated to 1 of 3 AFC treatments. Within each AFC treatment, heifers were randomly assigned to 1 of 3 LWFC treatments. From 16 weeks of age until first calving, heifers in all groups grazed pasture and were provided with supplementary feed when the quantity and quality of pasture was inadequate to meet growth requirements. Mean AFC and LWFC achieved were 25.1 ± 0.121, 29.9 ± 0.11 and 33.9 ± 0.09 months and 498 ± 4.09, 549 ± 5.40 and 595 ± 5.09 kg, respectively. As AFC increased, total production over the first 3 lactations increased. For each month's delay in AFC an extra 56.7 L milk, 1.78 kg milk fat, 1.45 kg milk protein and 3.23 kg fat + protein over the first 3 lactations was produced but by the third lactation the response was minimal. By end of third lactation the remaining heifers that calved at 25.1 months AFC were producing similar amounts to those that calved at the older AFC. As LWFC increased from 498 to 595 kg, production over the first 3 lactations increased. The response to an extra kilogram increase in LWFC was 4.82 L milk, 0.20 kg milk fat, 0.18 kg milk protein and 0.38 kg fat + protein over the first 3 lactations. The greatest benefit was when LWFC increased from 498 to 549 kg. Increasing LWFC from 549 to 595 kg did not significantly increase milk, milk fat and milk protein yields from the second to third lactation. The combined effects of AFC and LWFC indicated that to reduce the negative effects on production due to decreasing AFC, LWFC would have to increase by 7.2, 2.9 and 2.2 kg for each month decrease in AFC (for milk, fat and protein production, respectively). By the end of the third lactation, only 58 heifers remained in the herd. The number of heifers remaining within the 9 groups ranged from 4 to 10. Increasing LWFC while decreasing AFC reduced the chances of a heifer remaining in the herd but this may have been biased by the feeding regime imposed during lactation. Responses to increasing AFC decreased as the number of lactations increased, indicating that heifers calving at younger AFC produce similar amounts to their older herd-mates by the end of third lactation. Increasing LWFC from 498 to 549 kg had the greatest benefits for yield, indicating a possible maximum LWFC of 549 kg for our study. Therefore, the negative effects due to decreasing AFC can be offset in part, by increasing LWFC. However, on-farm resources and ultimately milk price will determine the choice of combination of AFC and LWFC.

Effects of Ionizable Residues on the Absorption Spectrum and Initial Electron-Transfer Kinetics in the Photosynthetic Reaction Center of Rhodobacter sphaeroides

Effects of ionizable amino acids on spectroscopic properties and electron-transfer kinetics in the photosynthetic reaction center (RC) of Rhodobacter sphaeroides are investigated by site-directed mutations designed to alter the electrostatic environment of the bacteriochlorophyll dimer that serves as the photochemical electron donor (P). Arginine residues at homologous positions in the L and M subunits (L135 and M164) are changed independently: Arg L135 is replaced by Lys, Leu, Glu, and Gln and Arg M164 by Leu and Glu. Asp L155 also is mutated to Asn, Tyr L164 to Phe, and Cys L247 to Lys and Asp. The mutations at L155, L164, and M164 have little effect on the absorption spectrum, whereas those at L135 and L247 shift the long-wavelength absorption band of P to higher energies. Fits to the ground-state absorption and hole-burned spectra indicate that the blue shift and increased width of the absorption band in the L135 mutants are due partly to changes in the distribution of energies for the zero-phonon absorption line and partly to stronger electron-phonon coupling. The initial electron-transfer kinetics are not changed significantly in most of the mutants, but the time constant increases from 3.0 +/- 0.2 in wild-type RCs to 4.7 +/- 0.2 in C(L247)D and 7.0 +/- 0.3 ps in C(L247)K. The effects of the mutations on the solvation free energies of the product of the initial electron-transfer reaction (P(+)) and the charge-transfer states that contribute to the absorption spectrum ( and ) were calculated by using a distance-dependent electrostatic screening factor. The results are qualitatively in accord with the view that electrostatic interactions of the bacteriochlorophylls with ionized residues of the protein are strongly screened and make only minor contributions to the energetics and dynamics of charge separation. However, the slowing of electron transfer in the Cys L247 mutants and the blue shift of the spectrum in some of the Arg L135 and Cys L247 mutants cannot be explained consistently by electrostatic interactions of the mutated residues with P and B(L); we ascribe these effects tentatively to structural changes caused by the mutations.

Application of TEPC microdosimetry to boron neutron capture therapy

Boron neutron capture therapy (BNCT) is a bimodal radiation therapy used primarily for highly malignant gliomas. Tissue-equivalent proportional counter (TEPC) microdosimetry has proven an ideal dosimetry technique for BNCT, facilitating accurate separation of the photon and neutron absorbed dose components, assessment of radiation quality and measurement of the BNC dose. A miniature dual-TEPC system has been constructed to facilitate microdosimetry measurements with excellent spatial resolution in high-flux clinical neutron capture therapy beams. A 10B-loaded TEPC allows direct measurement of the secondary charged particle spectrum resulting from the BNC reaction. A matching TEPC fabricated from brain-tissue-equivalent plastic allows evaluation of secondary charged particle spectra from photon and neutron interactions in normal brain tissue. Microdosimetric measurements performed in clinical BNCT beams using these novel miniature TEPCs are presented, and the advantages of this technique for such applications are discussed.

Reduction of enteric microorganisms at the Upper Occoquan Sewage Authority Water Reclamation Plant

The Upper Occoquan Sewage Authority (UOSA) Water Reclamation Plant, Centreville, Virginia, is a state-of-the-art wastewater treatment plant that was created to treat area wastewater and provide protection for the Occoquan Reservoir. This study investigated UOSA's unit processes as barriers to pathogenic as well as altemative and traditional-indicator microorganisms. Samples were collected once a month for 1 year from eight sites within UOSA's advanced wastewater reclamation plant. The eight sites were monitored for indicator bacteria total and fecal coliforms, enterococci, Clostridium, coliphage (the virus that infects Escherichia coli), human enteroviruses, and enteric protozoa. Overall, the plant was able to achieve a 5- to 7-log10 reduction of bacteria, 5-log10 reduction of enteroviruses, 4-log10 reduction for Clostridium, and 4.6-log10 reduction of protozoa. Total coliforms, enterococci, Clostridium, coliphage, Cryptosporidium, and Giardia were all detected in four or fewer samples of the final effluent. No enteroviruses or fecal coliforms were detected in the final effluent. The microbiological quality of reclaimed water and the reservoir water were compared. In every case, the treated wastewater was of a better quality than the ambient water in the reservoir, thus indicating that the reclaimed water will not adversely affect the water quality for downstream users.

A pilot survey of social work services in pediatric primary care programs in urban teaching hospitals

OBJECTIVE

To determine the current status of social work presence in pediatric primary care clinics in urban teaching hospitals.

DESIGN

Survey instrument mailed to the medical directors of outpatient pediatrics in the major pediatric teaching hospital of approved residency programs in the 100 largest metropolitan areas in the United States.

RESULTS

Sixty responses (60%) were received. Eighty percent of practices reported having on-site social work services, with a median of 14,805 annual clinic visits per social work full-time equivalent. Ninety-five percent of respondents considered on-site social work services in pediatric primary care to be important, whereas half of respondents considered social work services "less than adequate" at their site, and most of these felt this inadequacy had led to additional hospital visits or other adverse outcomes. There were no significant associations of reported adequacy of social work services with any characteristics of hospital, practice, or population.

CONCLUSION

Pediatric primary care clinicians at teaching hospitals consider on-site social work services to be important, but most report these services are less than adequate in their practices, and for many, adequacy has declined.

Developing a community-specific health-related quality of life (HRQOL) questionnaire for asthma: the Asthma-Specific Quality of Life Questionnaire for Native American Adults (AQLQ-NAA)

The Asthma Quality of Life Questionnaire for Native American Adults (AQLQ-NAA) was developed by modifying the Asthma Quality of Life Questionnaire-Marks (AQLQ-M) using the focus group technique. The 19-item AQLQ-NAA has emphasis on restrictions in social, community, and cultural activities. Higher scores indicate a better quality of life. The modified questionnaire was administered to a sample of 51 Native American adults with asthma at the Albuquerque USPHS Indian Hospital and its affiliated field clinics. Principal components analysis identified three domains with eigenvalues greater than 1.00: Community and Social Restrictions (CSR), Psychological Impact (PIM), and Symptoms (SYM). Cronbach's coefficient alpha for the AQLQ-NAA was 0.95 and ranged from 0.82 to 0.93 for the individual domains, indicating good internal consistency. The AQLQ-NAA score correlated negatively and significantly to urgent care visits, physician visits, and total number of medications taken for asthma in the past 6 and 12 months (p < 0.05). Additionally, the AQLQ-NAA score was correlated positively and significantly to medication adherence in the past 6 and 12 months (p < 0.05). Similar patterns of correlations were found with all three domain scores. These results indicated that there is evidence for the construct validity of the AQLQ-NAA and its domains. The AQLQ-NAA should provide a useful measure of HRQOL in asthma-specific medical interventions for the population in which it was developed.

Effects of age and liveweight at first calving on first lactation milk, protein and fat yield of Friesian heifers

This paper reports on both the individual and combined effects of age (AFC) and liveweight (LWFC) at first calving for Australian Holstein–Friesian heifers on first lactation production. One hundred and thirty-five Australian Holstein–Friesian heifers were allocated to 1 of 3 AFC treatments. Within each AFC treatment, heifers were randomly assigned to 1 of 3 LWFC treatments. Heifers in all groups grazed pasture and were supplemented when the quantity and quality of pasture was inadequate to meet growth requirements. Mean AFC and LWFC achieved were 25.1, 29.9 and 33.9 months and 498, 549 and 595 kg, respectively. Mean liveweight gains from 16 weeks of age to calving ranged from 0.45 to 0.71 kg/day, depending on treatment. The heifers calving at 33.9 months of age produced 6.6 and 12.3% more milk, 6.3 and 11.9% more protein and 5.4 and 12.2% more fat than those calving at 29.9 and 25.1 months of age at the end of their first 300 day lactation, respectively. The lower production of the younger cows was associated with decreased daily output rather than by shorter lactation length. Heifers averaging 595 kg at first calving produced 5.5% more milk, 8.4% more protein and 11.4% more fat than those averaging 498 kg in first lactation, respectively. The heifers averaging 621 kg LWFC and 34 months AFC had the highest production of the 9 treatment groups. Production was increased by 5.35 L milk, 0.19 kg protein and 0.23 kg fat for an additional 1 kg LWFC, respectively. For each month delay in AFC, production was increased by 66.7 L milk, 1.87 kg protein and 2.36 kg fat, respectively. The combined effects of AFC and LWFC showed that to offset the negative effects of a 1 month reduction in AFC on milk, protein and fat yields in first lactation, LWFC would have to be increased by 8.1, 4.0 and 4.5 kg, respectively. Under the conditions of this experiment, maximum milk, protein and fat were estimated to be achieved at 559, 563 and 568 kg liveweight at first calving, respectively.

Detection of viral pathogens by reverse transcriptase PCR and of microbial indicators by standard methods in the canals of the Florida Keys

In order to assess the microbial water quality in canal waters throughout the Florida Keys, a survey was conducted to determine the concentration of microbial fecal indicators and the presence of human pathogenic microorganisms. A total of 19 sites, including 17 canal sites and 2 nearshore water sites, were assayed for total coliforms, fecal coliforms, Escherichia coli, Clostridium perfringens, enterococci, coliphages, F-specific (F(+)) RNA coliphages, Giardia lamblia, Cryptosporidium parvum, and human enteric viruses (polioviruses, coxsackie A and B viruses, echoviruses, hepatitis A viruses, Norwalk viruses, and small round-structured viruses). Numbers of coliforms ranged from <1 to 1, 410, E. coli organisms from <1 to 130, Clostridium spp. from <1 to 520, and enterococci from <1 to 800 CFU/100 ml of sample. Two sites were positive for coliphages, but no F(+) phages were identified. The sites were ranked according to microbial water quality and compared to various water quality standards and guidelines. Seventy-nine percent of the sites were positive for the presence of enteroviruses by reverse transcriptase PCR (polioviruses, coxsackie A and B viruses, and echoviruses). Sixty-three percent of the sites were positive for the presence of hepatitis A viruses. Ten percent of the sites were positive for the presence of Norwalk viruses. Ninety-five percent of the sites were positive for at least one of the virus groups. These results indicate that the canals and nearshore waters throughout the Florida Keys are being impacted by human fecal material carrying human enteric viruses through current wastewater treatment strategies such as septic tanks. Exposure to canal waters through recreation and work may be contributing to human health risks.

Spinal cord hamartoma: case report

OBJECTIVE AND IMPORTANCE

Spinal cord hamartomas are infrequently mentioned in the literature. The authors present a unique report detailing the clinical presentation of a spinal cord hamartoma, with supporting radiographic and pathological data.

CLINICAL PRESENTATION

A 26-year-old man presented with progressive right upper extremity weakness. Imaging studies revealed an exophytic cervical spinal cord mass.

INTERVENTION

Open biopsy was undertaken and revealed tethering of the lesion to the dura. A pathological examination revealed a spinal cord hamartoma.

CONCLUSION

The patient's symptoms improved postoperatively, suggesting that tethering of the spinal cord was responsible for the symptoms. Although unusual, hamartoma should be included in the differential diagnosis of an exophytic spinal cord lesion.

Care pathways. Paving the way

Care pathways are most commonly used in acute trusts and private hospitals, according to a survey by the National Pathway Association. Orthopaedics is the specialty most likely to employ pathways, followed by surgery, medicine and care of elderly people. A third of respondents found the tool helped control costs, but a similar number found it did not. Setting and implementing standards of care and improving communication between staff are the most commonly reported benefits of using care pathways.

Comparison of Detection Methods for Citrus Tristeza Virus in Field Trees During Months of Nonoptimal Titer

Enzyme-linked immunosorbent assay (ELISA) can reliably detect citrus tristeza virus (CTV) in samples collected during approximately 6 months of a typical year. Two reverse transcriptase polymerase chain reaction (RT-PCR) methods (total nucleic acid extract and immunocapture based) were evaluated and compared to ELISA in order to develop a more sensitive assay for CTV. From May 1994 to October 1995, 6 sweet orange trees infected with CTV from each of 2 geographic areas (Riverside and the San Joaquin Valley) were tested monthly by each method. In the months of August (San Joaquin Valley samples) and September (Riverside and San Joaquin Valley samples) several of the trees had a significant loss of virus titer such that CTV was not reliably detected by ELISA. By contrast, the 2 PCR methods gave definitive positive results for CTV in samples collected during these months. Different tissue types were analyzed by each of the above assays. Petioles and midribs, both phloem-rich tissues, were each satisfactory for ELISA, while distal leaf tips did not always produce a positive result. All tissue types were equally efficient in producing a positive result in both PCR-based assays. The results of this study provide a basis for CTV testing by PCR in months when virus titer drops to a level generally unacceptable for using ELISA.