Hidden in plain sight

[Figure: see text].

A Disinhibitory Circuit for Contextual Modulation in Primary Visual Cortex

Context guides perception by influencing stimulus saliency. Accordingly, in visual cortex, responses to a stimulus are modulated by context, the visual scene surrounding the stimulus. Responses are suppressed when stimulus and surround are similar but not when they differ. The underlying mechanisms remain unclear. Here, we use optical recordings, manipulations, and computational modeling to show that disinhibitory circuits consisting of vasoactive intestinal peptide (VIP)-expressing and somatostatin (SOM)-expressing inhibitory neurons modulate responses in mouse visual cortex depending on similarity between stimulus and surround, primarily by modulating recurrent excitation. When stimulus and surround are similar, VIP neurons are inactive, and activity of SOM neurons leads to suppression of excitatory neurons. However, when stimulus and surround differ, VIP neurons are active, inhibiting SOM neurons, which leads to relief of excitatory neurons from suppression. We have identified a canonical cortical disinhibitory circuit that contributes to contextual modulation and may regulate perceptual saliency.

Feedback generates a second receptive field in neurons of the visual cortex

Animals sense the environment through pathways that link sensory organs to the brain. In the visual system, these feedforward pathways define the classical feedforward receptive field (ffRF), the area in space in which visual stimuli excite a neuron1. The visual system also uses visual context-the visual scene surrounding a stimulus-to predict the content of the stimulus2, and accordingly, neurons have been identified that are excited by stimuli outside their ffRF3-8. However, the mechanisms that generate excitation to stimuli outside the ffRF are unclear. Here we show that feedback projections onto excitatory neurons in the mouse primary visual cortex generate a second receptive field that is driven by stimuli outside the ffRF. The stimulation of this feedback receptive field (fbRF) elicits responses that are slower and are delayed in comparison with those resulting from the stimulation of the ffRF. These responses are preferentially reduced by anaesthesia and by silencing higher visual areas. Feedback inputs from higher visual areas have scattered receptive fields relative to their putative targets in the primary visual cortex, which enables the generation of the fbRF. Neurons with fbRFs are located in cortical layers that receive strong feedback projections and are absent in the main input layer, which is consistent with a laminar processing hierarchy. The observation that large, uniform stimuli-which cover both the fbRF and the ffRF-suppress these responses indicates that the fbRF and the ffRF are mutually antagonistic. Whereas somatostatin-expressing inhibitory neurons are driven by these large stimuli, inhibitory neurons that express parvalbumin and vasoactive intestinal peptide have mutually antagonistic fbRF and ffRF, similar to excitatory neurons. Feedback projections may therefore enable neurons to use context to estimate information that is missing from the ffRF and to report differences in stimulus features across visual space, regardless of whether excitation occurs inside or outside the ffRF. By complementing the ffRF, the fbRF that we identify here could contribute to predictive processing.

Reconsideration of blood donation testing strategy for human T-cell lymphotropic virus in Australia

BACKGROUND AND OBJECTIVES

Universal testing of blood donations for human T-cell lymphotropic virus (HTLV) in Australia may no longer be appropriate given the low prevalence of HTLV infection and the mitigating effect of universal leucodepletion for cellular components. This study aimed to determine the most appropriate HTLV testing strategy using the Risk-Based Decision-Making Framework for Blood Safety.

MATERIALS AND METHODS

The risk of HTLV transfusion-transmission using three testing strategies (universal, new-donor and no testing) and cost-effectiveness of the first two strategies were assessed using adaptations of published mathematical models.

RESULTS

The overall prevalence for 2004-2014 was three HTLV-positives per million donations. It was estimated that annually, universal testing incurred a cost of approximately AUD $3 million and prevented 83 HTLV-positive cellular components from being issued, and new-donor testing cost approximately $225 000 and prevented 81 components. The number of cases of transfusion-transmitted HTLV and HTLV-associated disease prevented per year by universal and new-donor testing was essentially equivalent. According to preset risk thresholds, the risk of transfusion-transmission was negligible for universal and new-donor testing, and minimal without testing.

CONCLUSION

Transfusion-transmission of HTLV is a minimal risk in Australia even without testing. However, any revision of testing strategy must consider not only risk and cost-effectiveness, but also stakeholder, ethical and regulatory perspectives. Considering all relevant criteria, new-donor testing is judged the optimal strategy because it is able to achieve almost the same outcomes as universal testing, at a fraction of the cost.

Stimulus relevance modulates contrast adaptation in visual cortex

A general principle of sensory processing is that neurons adapt to sustained stimuli by reducing their response over time. Most of our knowledge on adaptation in single cells is based on experiments in anesthetized animals. How responses adapt in awake animals, when stimuli may be behaviorally relevant or not, remains unclear. Here we show that contrast adaptation in mouse primary visual cortex depends on the behavioral relevance of the stimulus. Cells that adapted to contrast under anesthesia maintained or even increased their activity in awake naïve mice. When engaged in a visually guided task, contrast adaptation re-occurred for stimuli that were irrelevant for solving the task. However, contrast adaptation was reversed when stimuli acquired behavioral relevance. Regulation of cortical adaptation by task demand may allow dynamic control of sensory-evoked signal flow in the neocortex.

DOI:http://dx.doi.org/10.7554/eLife.21589.001

Refining the risk estimate for transfusion-transmission of occult hepatitis B virus

BACKGROUND AND OBJECTIVES

We previously published a model to estimate the residual risk (RR) for occult hepatitis B infection (OBI) in the absence of universal anti-HBc testing. To incorporate new information on the epidemiology of OBI, we describe model refinements and estimate a more accurate HBV RR due to OBI in Australia.

MATERIALS AND METHODS

In our original model, the OBI risk, p(OBI), was defined by the rate of 'non-detection' by the HBV DNA screening test in use, p(NAT non-detection), and the average infectivity of blood components from OBI donors, p(transmission). We revised the model by integrating three refinements: that donations with anti-HBs levels of >10 IU/l, or donations solely for manufactured plasma products, be excluded from the risk calculation, and an updated estimate of p(transmission).

RESULTS

Refining our OBI RR model resulted in a more than 10-fold reduction in the reported RR risk to recipients from OBI in our donor population. Based on the use of a common data set, the mean OBI RR risk decreased from 1 in 374 354 donations (95% CI: 1 in 191 940-1 072 681) to 1 in 3 984 033 (95% CI: 1 in 1 146 188-65 268 257) for the refined model.

CONCLUSION

Our model refinements provide a more realistic measure of the HBV RR in the donor population. Unlike the previous model, the new model demonstrates that the risk of HBV due to OBI in the Australian blood donor population is negligible, and further potentially cost-ineffective risk management strategies are not currently warranted.

Cotunneling Drag Effect in Coulomb-Coupled Quantum Dots

In Coulomb drag, a current flowing in one conductor can induce a voltage across an adjacent conductor via the Coulomb interaction. The mechanisms yielding drag effects are not always understood, even though drag effects are sufficiently general to be seen in many low-dimensional systems. In this Letter, we observe Coulomb drag in a Coulomb-coupled double quantum dot and, through both experimental and theoretical arguments, identify cotunneling as essential to obtaining a correct qualitative understanding of the drag behavior.

Universal Fermi liquid crossover and quantum criticality in a mesoscopic system

Quantum critical systems derive their finite-temperature properties from the influence of a zero-temperature quantum phase transition. The paradigm is essential for understanding unconventional high-Tc superconductors and the non-Fermi liquid properties of heavy fermion compounds. However, the microscopic origins of quantum phase transitions in complex materials are often debated. Here we demonstrate experimentally, with support from numerical renormalization group calculations, a universal crossover from quantum critical non-Fermi liquid behaviour to distinct Fermi liquid ground states in a highly controllable quantum dot device. Our device realizes the non-Fermi liquid two-channel Kondo state, based on a spin-1/2 impurity exchange-coupled equally to two independent electronic reservoirs. On detuning the exchange couplings we observe the Fermi liquid scale T*, at energies below which the spin is screened conventionally by the more strongly coupled channel. We extract a quadratic dependence of T* on gate voltage close to criticality, and validate an asymptotically exact description of the universal crossover between strongly correlated non-Fermi liquid and Fermi liquid states.

Re-evaluating the residual risk of transfusion-transmitted Ross River virus infection

BACKGROUND AND OBJECTIVES

Ross River virus (RRV) is an enveloped, RNA alphavirus in the same antigenic group as chikungunya virus. Australia records an annual average of 5000 laboratory-confirmed RRV infections. While RRV is currently geographically restricted to the Western Pacific, the capacity of arboviruses for rapid expansion is well established. The first case of RRV transfusion-transmission was recently described prompting a comprehensive risk assessment.

MATERIALS AND METHODS

To estimate the RRV residual risk, we applied laboratory-confirmed RRV notifications to two published models. This modelling generated point estimates for the risk of viraemia in the donor population, the risk of collecting a viraemic donation and the predicted number of infected components.

RESULTS

The EUFRAT model estimated the risk of infection in donors as one in 95 039 (one in 311 328 to one in 32 399) to one in 14 943 (one in 48 593 to one in 5094). The point estimate for collecting a RRV viraemic donation varied from one in 166 486 (one in 659 078 to one in 49 158) (annualized national risk) to one in 26 117 (one in 103 628 to one in 7729) (area of high transmission). The modelling predicted 8-11 RRV-infected labile blood components issued in Australia during a 1-year period.

CONCLUSION

Considering the uncertainty in the modelled estimates, the unknown rate of RRV donor viraemia and the low severity of any recipient RRV infection, additional risk management for RRV in Australia will initially be restricted to strengthening the messaging to donors regarding prompt reporting of any postdonation illnesses.

Design of a scanning gate microscope for mesoscopic electron systems in a cryogen-free dilution refrigerator

We report on our design of a scanning gate microscope housed in a cryogen-free dilution refrigerator with a base temperature of 15 mK. The recent increase in efficiency of pulse tube cryocoolers has made cryogen-free systems popular in recent years. However, this new style of cryostat presents challenges for performing scanning probe measurements, mainly as a result of the vibrations introduced by the cryocooler. We demonstrate scanning with root-mean-square vibrations of 0.8 nm at 3 K and 2.1 nm at 15 mK in a 1 kHz bandwidth with our design. Using Coulomb blockade thermometry on a GaAs/AlGaAs gate-defined quantum dot, we demonstrate an electron temperature of 45 mK.

HelioScan: a software framework for controlling in vivo microscopy setups with high hardware flexibility, functional diversity and extendibility

Intravital microscopy such as in vivo imaging of brain dynamics is often performed with custom-built microscope setups controlled by custom-written software to meet specific requirements. Continuous technological advancement in the field has created a need for new control software that is flexible enough to support the biological researcher with innovative imaging techniques and provide the developer with a solid platform for quickly and easily implementing new extensions. Here, we introduce HelioScan, a software package written in LabVIEW, as a platform serving this dual role. HelioScan is designed as a collection of components that can be flexibly assembled into microscope control software tailored to the particular hardware and functionality requirements. Moreover, HelioScan provides a software framework, within which new functionality can be implemented in a quick and structured manner. A specific HelioScan application assembles at run-time from individual software components, based on user-definable configuration files. Due to its component-based architecture, HelioScan can exploit synergies of multiple developers working in parallel on different components in a community effort. We exemplify the capabilities and versatility of HelioScan by demonstrating several in vivo brain imaging modes, including camera-based intrinsic optical signal imaging for functional mapping of cortical areas, standard two-photon laser-scanning microscopy using galvanometric mirrors, and high-speed in vivo two-photon calcium imaging using either acousto-optic deflectors or a resonant scanner. We recommend HelioScan as a convenient software framework for the in vivo imaging community.

Pseudospin-resolved transport spectroscopy of the Kondo effect in a double quantum dot

We report measurements of the Kondo effect in a double quantum dot, where the orbital states act as pseudospin states whose degeneracy contributes to Kondo screening. Standard transport spectroscopy as a function of the bias voltage on both dots shows a zero-bias peak in conductance, analogous to that observed for spin Kondo in single dots. Breaking the orbital degeneracy splits the Kondo resonance in the tunneling density of states above and below the Fermi energy of the leads, with the resonances having different pseudospin character. Using pseudospin-resolved spectroscopy, we demonstrate the pseudospin character by observing a Kondo peak at only one sign of the bias voltage. We show that even when the pseudospin states have very different tunnel rates to the leads, a Kondo temperature can be consistently defined for the double quantum dot system.

Estimating the risk of blood donation associated with HIV risk behaviours

A blood donor questionnaire and declaration, with deferral of potential donors at a higher risk of blood-borne infections, was introduced in Australia in the mid-1980s to reduce the risk of donation of HIV-infected blood. However, the absolute risk of HIV transmission through blood donation from high-HIV-risk donors has not been estimated. This study presents a new method of assessing the risk posed to the blood supply by selected HIV risk behaviours. A model was developed to estimate the probability of blood donation during the window period for HIV infection. Five scenarios for blood donors were considered: (1) men who have sex with men (MSM), (2) men who have sex with women in Australia, (3) women who have sex with partners from countries with a high HIV prevalence, (4) men who have sex with commercial sex workers in Australia and (5) people injecting drugs used once in a year. Those estimated to be at highest risk of becoming infected and donating in the window period were MSM. Women who have sex with men from countries of high HIV prevalence are at greater risk than men who have sex with female sex workers from Australia. These three groups under current Australian guidelines are deferred from donating blood for 12 months. In Australia, a single episode of injecting drug use is associated with very low risk of HIV transmission. The model presented in this study can be used to assess the impact of selected individual risk behaviours on the safety of the blood supply.

Sex differences in object location memory and spatial navigation in Long-Evans rats

In both humans and rodents, males typically excel on a number of tasks requiring spatial ability. However, human females exhibit advantages in memory for the spatial location of objects. This study investigated whether rats would exhibit similar sex differences on a task of object location memory (OLM) and on the watermaze (WM). We predicted that females should outperform males on the OLM task and that males should outperform females on the WM. To control for possible effects of housing environment, rats were housed in either complex environments or in standard shoebox housing. Eighty Long-Evans rats (40 males and 40 females) were housed in either complex (Complex rats) or standard shoebox housing (Control rats). Results indicated that males had superior performance on the WM, whereas females outperformed males on the OLM task, regardless of housing environment. As these sex differences cannot be easily attributed to differences in cognitive style related to linguistic processing of environmental features or to selection pressures related to the hunting gathering evolutionary prehistory of humans, these data suggest that sex differences in spatial ability may be related to traits selected for by polygynous mating strategies.

Residual risk of transfusion transmitted human immunodeficiency virus, hepatitis B virus, hepatitis C virus and human T lymphotrophic virus

BACKGROUND

The risk of transfusion transmitted viral infection is now so low that mathematical modelling is required to estimate the residual risk. The first national viral risk estimates for hepatitis B virus (HBV), human immunodeficiency virus (HIV) and hepatitis C virus (HCV) were recently published by the Australian Red Cross Blood Service. Using several refinements to the original methodology, as well as an additional 2 years of data, new risk estimates have been derived.

METHODS

Viral screening data for Australian donors for 2000/2003 were retrospectively analysed. The data were applied to three published models to estimate the residual risk of transmitting HIV, HBV, HCV or human T lymphotrophic virus (HTLV) by blood transfusion in Australia.

RESULTS

Applying the three models to HBV, HIV and HCV, three point estimates of the residual risk per unit were calculated for each virus. The median point estimates were 1 in 1,339,000 for HBV, 1 in 1 in 7,299,000 for HIV, and 1 in 3,636,000 for HCV. Although the HTLV risk could not be equivalently calculated because of the lack of incident infection it was estimated to be considerably less than 1 in 1,000,000 using a separate method.

CONCLUSIONS

The most current and accurate estimate of residual risk of viral transmission in Australia has been provided in the present study. The residual risk in Australia is exceptionally small, continuing to decrease and is generally less than European or US risk estimates. These new estimates demonstrate that for viral transmission the Australian blood supply is amongst the safest in the world, and provide a basis for evaluating the cost benefit of future viral testing methodologies.

The efficacy of a malarial antibody enzyme immunoassay for establishing the reinstatement status of blood donors potentially exposed to malaria

BACKGROUND AND OBJECTIVES

The two key objectives of the study were, first, to evaluate the sensitivity and specificity of a recombinant antigen-based malarial enzyme-linked immunoassay (EIA) and, second, to estimate the risk associated with implementing this test with a shortened cellular component restriction period (6 months rather than the standard 12-36 months) for blood donors with a malarial risk exposure.

MATERIALS AND METHODS

Blood donors were recruited into four distinct groups [non-exposed (control), malarial area 'visitors', 'residents' and 'previous infection') and screened by using the Newmarket malarial antibody EIA. Assay specificity was evaluated in unexposed blood donors, and sensitivity was determined in acute clinical samples.

RESULTS

No parasitaemic donors were detected amongst 337 malarial 'visitors' who had returned from a malaria-endemic area less than 6 months previously, or for 402 'visitors' or 'residents' who had returned from a malaria-endemic area more than 6 months previously. The incidence of malarial antibodies within the exposed blood donor groups was 1.33% (10/751). In acute clinical non-donor samples, the Newmarket EIA detected 106/108 (98.1; 93.5-99.5%) 'film' positive Plasmodium falciparum infections and 12/12 (100, 75.7-100.0%) P. vivax infections. The estimated additional risk exposure of the proposed new strategy was one infectious P. falciparum donation per 175 years or 1 per 4.2 years for P. vivax.

CONCLUSIONS

The study findings support the efficacy and safety of a targeted screening strategy combining antibody screening with a 6-month cellular component restriction period for donors with a declared malarial risk.

Variant Creutzfeldt-Jakob disease in Australian blood donors: estimation of risk and the impact of deferral strategies

BACKGROUND AND OBJECTIVES

In Australia, a policy of deferring donors who have lived in the UK for longer than 6 months between 1980 and 1996 has been instituted to reduce the theoretical risk of transmitting variant Creutzfeldt-Jakob disease (vCJD) through the blood supply. The objective of this report was to refine estimates of the possible risks and benefits of donor-deferral strategies that are aimed at avoiding transmission of vCJD.

MATERIALS AND METHODS

Estimates of the effect of donor deferral on the blood supply in Australia were based on a 1998 survey of blood donors. The number of donations from donors potentially infected with vCJD and excluded by donor deferral was estimated based on published estimates of the size of the vCJD epidemic in the UK and assuming that the risk of vCJD in Australian blood donors was proportional to the time lived in the UK between 1980 and 1996. The possible increased number of blood donations that were infected with human immunodeficiency virus (HIV), hepatitis C virus (HCV) or hepatitis B virus (HBV) and made during a window period (as a result of increased donations from first-time donors) was estimated using published methods.

RESULTS

A strategy of deferring donations in Australia from people who have lived in the UK for 6 months or longer, between 1980 and 1996, was estimated to result in exclusion of 5.3% of all blood donations, corresponding to 50 100 donations in 1998. It was estimated that the annual number of blood donations made by donors potentially infected with vCJD is 1.15 (range 0.02--31.1, based on the uncertainty in the UK prevalence estimate). Donor deferral was estimated to remove 0.92 (range 0.02--25.1) of these donations. Replacement of 33%, 50% and 100% of excluded donations by donations from first-time donors, was estimated to result in an increase of 0.0010, 0.0019 and 0.0044, respectively, of HIV-infected donations per year donated during the window period; in an increase of 0.021, 0.038 and 0.089, respectively, of HCV-infected donations per year; and in an increase of 0.18, 0.33 and 0.76, respectively, of HBV-infected donations per year.

CONCLUSIONS

The large uncertainties involved in these analyses mean that estimates must be interpreted cautiously, but the data does suggest that donor deferral may exclude more donations from donors potentially infected with vCJD than the corresponding increase, caused by donor replacement, of window-period donations possibly infected with HIV, HCV or HBV.

Geographical distribution of hepatitis C virus genotypes in blood donors: an international collaborative survey

The frequency of infection with the six classified major genotypes of hepatitis C virus (HCV) was investigated in 447 infected volunteer blood donors from the following nine countries: Scotland, Finland, The Netherlands, Hungary, Australia, Egypt, Japan, Hong Kong, and Taiwan. Viral sequences in plasma from blood donors infected with HCV were amplified in the 5'-noncoding region and were typed by restriction fragment length polymorphism analysis. Electrophoresis of DNA fragments produced by cleavage with HaeIII-RsaI and ScrFI-HinfI allowed HCV types 1 (or 5), 2, 3, 4, and 6 to be identified. Further analysis with MvaI-HinfI allowed sequences of the type 5 genotype to be distinguished from sequences of the type 1 genotype. Types 1, 2, and 3 accounted for almost all infections in donors from Scotland, Finland, The Netherlands, and Australia. Types 2 and 3 were not found in the eastern European country (Hungary), where all but one of the donors were infected with type 1. Donors from Japan and Taiwan were infected only with type 1 or 2, while types 1, 2, and 6 were found in those from Hong Kong. HCV infection among Egyptians was almost always by type 4. Donors infected with HCV type 1 showed broad serological reactivity with all four antigens of the second generation Chiron RIBA-2 assay (Chiron Corporation, Emeryville, Calif.), while infection with divergent HCV genotypes elicited antibodies mainly reactive to c22-3 and c33c. Reactivities with antibodies 5-1-1 and c100-3 were infrequent and were generally weak, irrespective of the geographical origin of the donor. Because the envelope region of HCV is even more variable than the NS-4 region, it is likely that vaccines based on these proteins need to be multivalent and perhaps specifically adapted for different geographical regions.

Zidovudine (AZT) therapy in children with HIV infection: the Australian experience

Fifteen children (11 males and four females), on oral Zidovudine (AZT) for symptomatic HIV infection were studied retrospectively. Twelve acquired HIV via blood products, two from vertical transmission (maternal intravenous needle sharing) and one through breast feeding. Their mean age at the start of therapy was 8.6 years (s.d. 4.4 years, range 1.8-15.3 years). The main indications for therapy were failure to thrive (FTT) in 10, recurrent respiratory tract infections (RRTI) in eight, and developmental delay (DD) in one, with overlapping indications being Pneumocystis carinii pneumonia (PCP) in one and pulmonary lymphoid hyperplasia (PLH) in two. The mean commencement dose was 24 mg/kg per day orally in 3-6 divided doses (range 16-35 mg/kg per day). The duration of therapy was 2 weeks-2 1/2 years. Significant improvement in growth was observed by 2 months; at 6 months, growth was sustained in these otherwise ill children, with only two falling below pretreatment weight. Decrease in the frequency of RRTI based on subjective reports of the attending clinicians was observed in seven of the eight evaluable children still on therapy. Improvement in PCP and PLH occurred in two children and modest improvement was subjectively reported in PLH in one while still early in the course of therapy. Overall, AZT was well tolerated. Dose modifications were for neutropenia in three (of which only two were drug related), rapidly falling neutrophil count in one, anaemia in two (with concurrent history of chronic gastrointestinal tract blood loss in one), severe GIT irritation in one and transient sedation in one. Seven opportunistic infections were reported (three in the same patient) of which two occurred following cessation of therapy, one after only 2 weeks of therapy, and one had not been on primary prophylactic therapy. Three deaths occurred, one associated with opportunistic infections and two while off therapy (one respiratory failure, one PCP).

Microvascular free flap reconstruction for head and neck defects

In a three-year period, 53 microvascular free-tissue grafts were performed on 51 patients to repair defects following major head and neck ablative surgery or trauma. The vast majority were done at the time of tumor resection. The remainder were done as secondary operations after resection or injury. The choice of free flap was dictated by the reconstructive needs of the patient and donor site availability. Fifty-two (98%) of 53 free-tissue transfers were successful with one failure resulting from venous thrombosis. Complications were noted in 16 of 53 flaps. The majority of these complications were in flaps used to replace bony defects or oropharyngeal resections. Although free flaps may appear to be more risky than traditional forms of reconstruction, they offer the surgeon a greater spectrum of reconstructive options. Limitations of the use of free flaps result only from lack of technical skills and specialized equipment.

Voice restoration after laryngopharyngoesophagectomy

Although various methods of alaryngeal communication after laryngectomy have been described, little attention has been given to voice restoration after laryngopharyngoesophagectomy. This article deals with our experience reconstructing the hypopharynx and cervical esophagus in five patients by the use of microvascular free tissue grafts. Voice restoration procedures with use of a Blom-Singer prostheses were used uniformly and resulted in the attainment of functional voice in each patient. It is our feeling that this method should be used equally in patients undergoing both traditional laryngectomy and laryngopharyngoesophagectomy.

Population-based epidemiology of human immunodeficiency virus infection in Western Australia. Western Australian AIDS Advisory Committee

A total of 328 cases of infection with human immunodeficiency virus (HIV) in Western Australia in 1983-1987 was studied with respect to demographic factors, the risk profile, the clinical progression of disease, the utilization of inpatient services and trends in incidence over time. The crude incidence rates were 8.8 cases/100,000 person-years in men and 0.4 cases/100,000 person-years in women. Age-specific rates peaked at 25 to 29 years of age in men. The risk of HIV infection was associated with metropolitan residence, low socioeconomic level, and two specific occupational groups. Homosexual and bisexual men constituted 86% of all cases; the incidence rate of HIV infection in such men was approximately 1000-times higher than was the incidence rate by apparent sexual transmission in heterosexual persons. However, the proportion of cases that occurred in women or that apparently was caused by heterosexual sexual transmission increased from zero in 1983-1984 to 7.5% and 5.4%, respectively, in 1987. After two years of follow-up, 71% of preclinical (category-C) patients had developed signs, symptoms or evidence of immune dysfunction, and 12% of those patients with lymphadenopathy or with other early clinical features of disease (category-B) had progressed to the acquired immunodeficiency syndrome (AIDS). At 21 months of follow-up, the survival rate with AIDS was 9%. Patients with AIDS utilized an average of 68.9 short-stay hospital bed-days per person-year, while category-B patients used 11.5 hospital bed-days per person-year. Notifications of HIV infection increased each year from 1983 to 1986, but fell by 22% in 1987. The latter may have been as a result of chance, a screening artefact or a real reduction in the incidence rate.

Evaluation of reconstructive techniques of oropharyngeal defects

Despite recent advances in radiation therapy and chemotherapy, surgical procedures remain the primary modality of head and neck cancer therapy. Adequate surgical resection frequently requires the removal of significant amounts of tissue. The primary concern of the reconstructive surgeon is the restoration of a functional aerodigestive tract. In addition to the prolongation of life, the quality of that life should be taken into consideration. The records of 25 patients undergoing oropharyngeal reconstruction for tumors stage 3 or 4 in the 4-year period from 1983 to 1986 were reviewed. After surgical extirpation, reconstruction was performed using either a pectoralis major musculocutaneous flap or a microvascular free flap. Results were evaluated with emphasis on both the intraoperative and postoperative course. The length of the procedure, time of initiation of oral feedings, time of decannulation, postoperative complications, time of discharge, and quality of life after discharge were considered. Those patients reconstructed with microvascular free flaps were able to tolerate oral feedings sooner and were discharged sooner than those patients reconstructed with pectoralis musculocutaneous flaps. In addition, the patients with pectoralis flaps were twice as likely to have local complications (e.g., superficial wound infection, fistula) as those with free flaps. The quality of the patient's life with respect to deglutition and intelligibility of speech was likewise better for those patients reconstructed with microvascular free flaps. The explanation of these results is presented.

Increased complications and prolonged hospital stay in elderly cardiac surgical patients with low serum albumin

Cardiac surgery in elderly patients is associated with acceptable operative mortality but an increased complication rate. Malnutrition is common in the elderly and may adversely affect surgical outcome. To determine the effect of hypoalbuminemia on postoperative complications, 92 patients greater than or equal to 75 years (range 75 to 90) undergoing a variety of major cardiac surgical procedures were evaluated. Thirteen patients (14%) had a serum albumin level less than 3.5 g/dl preoperatively. Compared to patients with normal albumin, hypoalbuminemic patients had an increased frequency of postoperative confusion, congestive heart failure, low cardiac output, renal dysfunction and gastrointestinal complications (all p less than 0.05). Mean postoperative length of stay was markedly prolonged in these patients (27 vs 12 days; p less than 0.001), and mortality also tended to be higher (31 vs 13%; p = 0.11). Using multivariate analysis, albumin less than 3.5 g/dl was the most powerful predictor of postoperative renal dysfunction (p less than 0.01), and was also an independent predictor of increased length of stay (p less than 0.01) and gastrointestinal disorders (p less than 0.05). Thus, hypoalbuminemia is a powerful indicator of an increased risk of perioperative complications in elderly patients undergoing cardiac surgery. Increased attention to nutritional factors is warranted in these patients.

Rigid internal fixation and vascularized bone grafting in mandibular reconstruction

The technique of mandibular reconstruction utilizing rigid internal fixation and vascularized bone grafts has been described. This type of repair should be considered in all patients undergoing mandibular resection for head and neck malignancies. Although no ideal method of reconstruction has yet been described, it appears that rigid internal fixation combined with vascularized bone grafts most satisfactorily fulfills the requirements associated with reconstruction of jaw defects.

Anatomic reconstruction and functional rehabilitation of oromandibular defects with rigid internal fixation

Fifteen consecutive patients undergoing extensive surgery for head and neck cancer involving the oral cavity and oropharynx were reconstructed using the technique of rigid internal fixation combined with various vascularized flaps. The follow-up ranged from 6 to 18 months. Modifications in various myocutaneous or vascularized free flaps combined with an analysis of the radiation physics necessary to make this procedure a viable alternative for immediate and delayed mandibular reconstruction will be discussed. Consistently satisfactory functional and cosmetic results have been achieved.

Microvascular free-tissue transfer with rigid internal fixation for reconstruction of the mandible following tumor resection

The authors described their experience using rigid internal fixation techniques in combination with free microvascular tissue transfer for the immediate reconstruction of mandibular defects following tumor ablation. The technique allows immediate return of jaw motion and limited function while assuring maintenance of occlusion and reasonable cosmesis.

Hepatitis B markers in health care workers. The Newcastle study

Health care workers in the Royal Newcastle Hospital, in surrounding hospitals and pathology services, and in a large mental institution were surveyed to determine the prevalence of hepatitis B markers. The aim of the study was to identify the groups of workers at particular risk of contracting hepatitis B in order to determine which workers would benefit most from a programme of vaccination against hepatitis B. Although the prevalence of hepatitis B markers in the Newcastle health care workers was higher than that in the control subjects, this rate did not approach the high rates previously reported in overseas studies.

Prognosis in childhood epilepsy: additional follow-up of 148 children 15 to 23 years after withdrawal of anticonvulsant therapy

To evaluate the risk of relapse in children with epilepsy whose anticonvulsant therapy has been withdrawn after prolonged control, we studied 148 such children for 15 to 23 years or until relapse. Forty-one of the 148 patients (28 per cent) had recurrence of seizures; of these, 35 (85 per cent) had relapses within five years of drug withdrawal. Factors associated with an increased risk of relapse were a long duration of epilepsy before control, neurologic dysfunction, and jacksonian seizures or combinations of seizure types. We found no association between risk of recurrence and age at onset of epilepsy, total number of seizures before control, age at discontinuation of therapy, electroencephalographic abnormalities, or family history of epilepsy. We conclude that children who do not have the additional risk factors noted above have an excellent chance of remaining seizure free after the withdrawal of anticonvulsant drugs.

[Loop suction biopsy of the urinary bladder]

During the last year we used a selective catheter cell aspiration method besides lavage cytology of the bladder. We used a special 7 Charr. Teflon catheter with a metal scraper at its tip. In our clinical experience we see the following advantages of selective catheter cell aspiration: 1. there are no artificial changes in cells caused by urine effects. 2. large and intact cell clusters can be aspirated from the bladder mucous membrane. 3. selective aspiration of cell clusters from suspicious areas of the bladder now is possible. Lavage urine samples include all kinds of cells of the whole urinary tract. No cystoscopic examination is necessary. In special cases we use selective catheter cell aspiration in addition to lavage urine for cytologic examination.

Coagulation abnormalities following intensive plasma exchange on the cell separator. II. Effects on factors I, II, V, VII, VIII, IX, X and antithrombin III

The effects of intensive plasma exchange on the circulating levels of coagulation factors I, II, V, VII, VIII, IX, X and antithrombin III were determined. During courses of daily exchange marked cumulative reductions of coagulation factors may occur, particularly in the case of factors I, II and X, although usually remaining above the levels considered adequate for haemostasis. The extent of cumulative reduction and subsequent recovery differed for patients with different diseases. While antithrombin III levels were reduced during plasma exchange the results suggest that this may be partly due to consumption as well as physical removal. The very low incidence of haemorrhagic sequelae and absence of thrombotic events following plasma exchange at this Centre is explained by the maintenance of adequate levels of coagulation factors and of antithrombin III even during courses of daily plasma exchange.

[Evaluation of cytomorphological parameters during hormonal therapy of prostatic carcinoma (author's transl)]

In 136 patients with prostatic carcinoma 544 aspiration biopsies were performed to study cytological signs of tumor regression caused by oestrogen therapy. For better interpretation a statistical evaluation of well defined regression signs in a constant number of cancer cells dependent on the tumor grading first was used. Additionally all data can be transferred to time diagrams. An approximate prediction of the future regression in cancer cells is possible.

Cryocautery of prostate

Cryocautery is a further development of cryosurgery of the prostate in patients at high risk. This new operative method combines both freezing and subsequent heating of the prostate. Cryocautery is performed without general or medullary anesthesia. Since 1975, 136 patients have been treated with this method; 88 per cent have had a good postoperative result. A follow-up examination after eighteen months shows 79 per cent of the patients with good results. The advantages of cryocautery are (1) more prostatic tissue becomes necrotic; (2) regeneration processes are suppressed for a long time; (3) no postoperative hemorrhage in the sloughing period; (4) sloughing of necrotic tissue begins after forty-eight hours; and (5) postoperative hospital stay can be reduced to one to two days.

[Cryocautery of the prostate. Experimental and clinical experiences]

We developed cryocautery in 1975. This new operation method combines both freezing and subsequent heating of the prostatic adenoma. Up to now 143 patients at high risk have been treated with cryocautery. For the operation itself no anesthesia is necessary. 87% of the patients had a "good" postoperative result. The second examination after two years shows 79% with a "good" result. The advantages of cryocautery are: more tissue becomes necrotic, no evidence of postoperative early and late bleeding, sloughing of necrotic tissue already after two days, postoperative hospital stay 1-2 days.

Coagulation abnormalities produced by plasma exchange on the cell separator with special reference to fibrinogen and platelet levels

Five patients with immunopathologic renal disease, 12 with malignant paraproteinaemia and one with myasthenia gravis underwent a total of 179 plasma exchanges on a continuous flow cell separator. Replacement fluids devoid of coagulation factors were used in 160 exchanges while 19 exchanges were replaced with Fresh Frozen Plasma. Coagulation screening was done immediately before and 30 min after each plasma exchange. Plasma fibrinogen concentrations fell to a mean of 25% of initial levels during individual exchanges. Sequential reduction to 10.7% was observed after five consecutive daily exchanges and in one patient fell to 1.2% after 10 daily exchanges. Low levels of fibrinogen could be maintained with daily or alternate daily exchanges. Platelet counts fell to a mean of 50% of pre-exchange levels during individual exchanges. Consecutive daily exchanges resulted in mean reductions to 20.7% after 5 d, but further reductions were not observed with longer periods of exchange. Platelet counts recovered to pre-exchange values during exchange intervals of 2 or more days. Mild clinical bleeding episodes, probably related to low platelet counts, occurred in one exchange in each of three patients. Haemostasis was rapidly achieved in these patients by infusions of platelet concentrates. Coagulation screening, including prothrombin ratio, thrombin time, reptilase time and partial thromboplastin time with kaolin showed progressively greater abnormalities as the intervals between exchanges shortened. The low incidence of clinical haemorrhagic episodes, three of 179 exchanges (2.2%), despite markedly abnormal coagulation parameters, emphasize the safety of the procedure even in moribund patients. We conclude that the use of FFP in intensive exchange programmes solely for the prevention of spontaneous haemorrhagic phenoma is unjustified.

Treatment of Goodpasture's disease by plasma exchange and immunosuppression

Three cases of Goodpasture's disease are described who were treated with intensive plasma exchange and immunosuppression. There was no improvement in renal function and the patients required chronic haemodialysis, but renal function did recover with treatment for recurrence of disease in a transplanted kidney. Anti-GBM antibody levels were not controlled and substantial reduction in fibrinogen and complement were only achieved with daily treatment. A controlled trial of this regime is urgently required.

Leukapheresis for papilloedema in chronic granulocytic leukaemia

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Phytohemagglutin-induced lymphocyte transformation in oral contraceptive users

Phytohemagglutin (PHA)-induced lymphocyte transformation (PILT) was determined in 217 women taking oral contraceptives and 203 control women by means of the uptake of 3H-thymidine into DNA of lymphocytes cultured in heterologous serum. Depressed PILT responses were observed in oral contraceptive users as compared with age-matched controls, and the magnitude of depression correlated with the duration of oral contraception and was inversely related to the clinical progestagenic potency of the component steroids. An additional group of 21 women, tested within 1 year (mean 3 months) of cessation of oral contraception, showed persistent depression of PILT responses. Suppression of lymphocyte transformation in autologous as compared with homologous, normal serum suggests that serum inhibitory factors amy be important. We found no evidence for a direct suppressive in vitro effect of synthetic estrogens and gestagens. The prevalence of autoantibodies in oral contraceptive users was similar to that in control subjects.