Spatial and temporal receptive-field analysis of the cats geniculocortical pathway

Receptive field (RF) properties of lateral geniculate (LGN) and cortical visual neurons were studied in cats using computer-controlled bar and edge stimuli. Responses to stationary presentations of an optimally oriented bright bar in an array of closely spaced RF positions provided detailed spatial and temporal information about RFs. Moving edge stimuli represent a more nearly normal viewing situation, and responses provide additional information for classifying RFs. Our results allow inferences about the nature of input connections to conical units. Responses of simple striate cells and X cells of LGN were similar to each other and quite different from those of complex and Y-LGN cells. Simple and X cells exhibited spatially segregated regions of excitation and inhibition and large shifts in response latency as a function of stimulus position. Both cell types showed spatially nonoverlapping regions of response (discharge zones) to moving bright and dark edges. These results provide correlational evidence that simple cells of striate cortex receive input predominantly from X-LGN cells. X-LGN cells respond to increases or decreases in local stimulus flux, depending on stimulus position, and via separate (from segregated RF areas) projections to the cortex determine contrast polarity of the cortical response. Complex cells, on the other hand, exhibited transient responses to both stimulus onset and removal. with a constant response latency across the entire RF. Results from the same test on Y-LGN cells were strikingly similar to those for complex cortical cells. However, complex cells show far more overlap in edge discharge zones than either on- or off-center Y-LGN cells. This comparison suggests spatially overlapping input to complex cells from both on-and off-center Y-LGN cells. A third type of cortical cell (in area 18) demonstrated edge and static-bar responses that strongly resembled those of either on-or off-center Y-LGN cells. Input to these parastriate cortical cells apparently derives from either on-or off-center Y-LGN cells. We believe that these units represent the parastnate equivalent of striate simple units in that they seem to receive inputs from spatially segregated RF areas, in this case of Y-LGN units.     

A comparison of the myocardial metabolic and haemodynamic changes produced by propofol-sufentanil and enflurane-sufentanil anaesthesia for patients having coronary artery bypass graft surgery

The purpose of this study was to compare propofol-sufentanil with enflurane-sufentanil anaesthesia for patients undergoing elective coronary artery bypass graft (CABG) surgery with respect to changes in (1) haemodynamic variables; (2) myocardial blood flow and metabolism; (3) serum cortisol, triglyceride, lipoprotein concentrations and liver function; and (4) recovery characteristics. Forty-seven patients with preserved ventricular function (ejection fraction greater than 40%, left ventricular end diastolic pressure less than or equal to 16 mmHg) were studied. Patients in Group A (n = 24) received sufentanil 0.2 microgram.kg-1 and propofol 1-2 mg.kg-1 for induction of anaesthesia which was maintained with a variable rate propofol (50-200 micrograms.kg-1.min-1) infusion and supplemental sufentanil (maximum total 5 micrograms.kg-1). Patients in Group B (n = 23) received sufentanil 5 micrograms.kg-1 for induction of anaesthesia which was maintained with enflurane and supplemental sufentanil (maximum total 7 micrograms.kg-1). Haemodynamic and myocardial metabolic profiles were determined at the awake-sedated, post-induction, post-intubation, first skin incision, post-sternotomy, and pre-cardiopulmonary bypass intervals. Induction of anaesthesia produced a larger reduction in systolic blood pressure in Group A (156 +/- 22 to 104 +/- 20 mmHg vs 152 +/- 26 to 124 +/- 24 mmHg; P less than 0.05). No statistical differences were detected at any other time or in any other variable including myocardial lactate production (n = 13 events in each group), time to tracheal extubation and time to discharge from the ICU. We concluded that, apart from hypotension on induction of anaesthesia, propofol-sufentanil anaesthesia produced anaesthetic conditions equivalent to enflurane-sufentanil anaesthesia for CABG surgery.     

Failure mechanisms of unicompartmental knee replacement: the impact of changes in operative technique and component design

Reliable unicompartmental knee replacement requires knowledge of the common failure mechanisms of this type of arthroplasty. The problem in the past has been loosening of components because of design flaws and technical failure. Whereas recent reports are very encouraging in terms of clinical results and enhanced durability of unicompartmental replacements, the current study confirms the observation that nonparallel orientation of femoral and tibial components is common and may produce excessive polyethylene wear and clinical failure. Newer unicompartmental designs with meniscal bearings may be the answer to this problem.     

Comparison of the early healing course of porous titanium with hydroxyapatite-coated porous titanium hip implants: clinical considerations for the use of hydroxyapatite coating in total hip replacement

The role of hydroxyapatite (HA) coating in the fixation of human total joint prostheses remains to be established. Results of animal studies have been favorable, showing very rapid bone formation with a corresponding increase in bone-implant bond strength. In addition, the quantity of bone may be increased. This study compared identical porous titanium primary total hip implants with and without HA in similar patient populations. All of these patients were healthy and reliable, and had optimal bone geometry and bone quality for cementless fixation. The purpose of the study was to contrast the sequence of events, in the first year after surgery, between the two implant groups to identify the contribution of HA to early patient function and early radiographic appearance of the prosthesis. No significant clinical difference could be demonstrated between the two groups at 1 year from surgery. However, the HA group progressed more rapidly when comparing clinical scores at 6 months (P = .0058), and appeared to demonstrate more rapid bone remodeling at 6 months on the femoral side, although this observation did not quite make statistical significance (P = .0618). There was no difference between the acetabular components during the course of this study.     

Restoration of bone stock in revision surgery of the femur

Three hundred and four femoral revisions were performed from 1987 to the end of 1990. All were done with cementless titanium calcar replacement prostheses, designed for proximal bone loading. Type III bone deficiencies were present in 160 femurs, all requiring supplemental cortical bone plates for bony augmentation. All grafts united and provided increased bone stock in the long term. Physiologic loading is important for graft remodeling and maturation. Hip scores have improved from an average Harris Hip Score of 44 to 84. Current survivorship at 10 years is 96%, and the revision rate is 3.2%. Thigh pain is mild in 3% of cases. There have been no late failures or distal lysis noted to date.

---

Résumé  De 1987 à 1990, on a procédéà 304 reprises de prothèse totale de hanche (PTH) associées à des implants fémoraux standard en alliage de titane non cimentés et spécifiquement étudié et réalisés pour bien s’adapter à la morphologie osseuse et à la résistance mécanique proximale. 160 cas de fémur nécessitèrent – vu la présence de perte de sustance osseuse de type III – la mise en place sur la corticale de plaque osseuse de remplacement afin d’augmenter et la repousse fémorale osseuse. On observe dans les cas de reprise de PTH, une amélioraton du recul moyen: ce dernier passait de 44 mois (selon l’échelle de le Harris Hip score) à 84 mois. A l’heure actuelle, le taux actuariel de survie des implant est de 96% à 10 ans avec un taux de reprise de 3.2%. On note la presence de douleur à la cuisse dans 3% des cas, mais à l’heure actuelle, on ne rapporte aucun échec tardif ni osteolyse distale.

---

---

Accepted: 7 December 1999     

Measurement of albumin and low molecular weight proteins in the urine of newborn infants using a cotton wool ball collection method

Objective : The aim of this study was to investigate the inter-relationship between urinary excretion of alpha-1-microglobulin (AIM), retinol-binding protein (RBP) and albumin in term and premature neonates, with urine collected into cotton wool balls and extracted by a novel method. Subjects and methods : Sixty-four infants were studied on the first day of life; 26 had been born at term (37–42 weeks gestation) and 38 prematurely (24–28 weeks n = 16, 29–36 weeks n = 22). Urine collected into cotton wool balls was analysed following a new detergent extraction method, which resulted in a recovery rate of 94–107% for albumin, AIM, RBP and creatinine. Results : Urinary protein excretion, expressed as a ratio to urinary creatinine, decreased significantly with increasing gestational age (24–28 weeks, 29–36 weeks, 37–42 weeks: albuminxreatinine ratio mg/mmol mean 96.9, 31.7, 19.3; AIM: creatinine ratio mg/mmol mean 99.3, 37.0, 7.8; RBP: creatinine ratio mg/mmol mean 16.2, 3.8, and <0.01, below the limit of detection, respectively). When results were corrected for birthweight, this gestation-associated effect was still present for A1M and RBP, but not for albumin. In premature infants there was a significant positive correlation between AIM: creatinine ratio and RBP: creatinine ratio ( r = 0.85), and also between albumin and both AIM and RBP ( r = 0.82 and 0.77). Conclusion : Increased excretion of AIM, RBP and albumin at earlier gestational ages is probably due to proximal tubular immaturity, although tubular damage and also glomerular dysfunction cannot be excluded as possible explanations.