Baseline factor VIII plasma levels and age at first bleeding in patients with severe forms of von Willebrand disease.

INTRODUCTION: von Willebrand disease (VWD) is the most common inherited bleeding disorder. The age of bleeding onset is highly variable, also in patients with similar degree of severity. AIM: The primary aim of this study was to evaluate whether baseline factor VIII (FVIII) plasma levels correlate with age at first bleeding in patients with extremely low levels of VWF:RCo (<6 IU dL(-1) ). METHODS: One hundred and three patients with VWF:RCo <6 IU dL(-1) (6 VWD1, 73 VWD2 and 24 VWD3) undergoing a medical examination between September 2010 and September 2013 were included. The relationship between baseline FVIII levels and age at first bleeding was tested in a multivariable linear regression model, adjusting for sex. RESULTS: The median age at first bleeding was lower in patients with VWD3 than in those with severe forms of VWD1 or VWD2 (1 year vs. 7 and 8 years, respectively, P < 0.0001). A positive non-linear relationship between FVIII levels and age at first bleeding was found, the latter increasing by 5 years for every 10 IU dL(-1) increase of FVIII (ß = 4.95 [95% CI: 2.02-7.87]) until levels of 30 IU dL(-1) , after which the age increased slowly. This relationship was not found in VWD 2A and 2B. In 65 patients (63%) there was a more than 6-month delay between bleeding onset and VWD diagnosis, with no difference over decades. CONCLUSIONS: Baseline FVIII plasma levels influence the age at bleeding onset in VWD patients with extremely low levels of VWF:RCo, except in those with types 2A and 2B.

Long-term prophylaxis in severe factor VII deficiency.

INTRODUCTION: The spectrum of bleeding problems in FVII deficiency is highly variable and FVII levels and causative genetic mutations correlate poorly with the bleeding risk. Long-term prophylaxis is generally initiated in order to prevent subsequent CNS bleeding after a first event or in patients with other major/ life threatening/ frequent bleeding symptoms as gastrointestinal bleeding or hemarthrosis. However few data are available in the literature regarding FVII prophylaxis and clinical decisions cannot be based on evidence. AIMS: We report the data available in the literature on FVII prophylaxis and our personal experience regarding three patients affected by severe FVII deficiency. METHODS: Specific papers on long-term prophylaxis in severe FVII deficiency were identified using the database, PUBMED. RESULTS: The most frequent indications for long-term prophylaxis were CNS bleeding (58%), hemartrosis (15%) and GI bleeding (9%). Patients were treated with various dosages and frequency. Prophylactic treatment with 10-30U/kg (pdFVII) or 20-30mcg/kg (rFVIIa) twice or three times/weeks was described to be effective. CONCLUSIONS: In the literature and in our experience, prophylaxis can be considered in patients with severe FVII deficiency and severe bleeding phenotype. A dose of 10-30U/kg (pdFVII) or 20-30 microg/kg (rFVIIa) twice or three times/week is usually administrated, but dose and frequency can be tailored based on the clinical follow-up of the patients. Since hemarthrosis is a frequent manifestation, a suggestion to improve the outcomes of patients with severe FVII deficiency is to monitor joint condition in order to identify early arthropathy that could be another indication to start secondary prophylaxis.

Orthopaedic surgery in patients with von Willebrand disease.

Patients with von Willebrand disease (VWD) may need orthopaedic surgery because of disabling chronic arthropathy due to recurrent joint bleeding. They may also require this surgery independently of their haemostasis disorder. Knowledge regarding the management of orthopaedic surgery in VWD is limited. Description of management of orthopaedic surgery in patients with VWD, based upon retrospective data collection and analysis of 32 orthopaedic procedures carried out over a period of 33 years in 23 patients was the aim of this study. Of 32 procedures, six were minor (three hand surgery, one foot surgery, two others) and 26 were major (seven joint replacements, nine arthroscopic procedures, two foot surgery, eight others). Twenty-two procedures were performed using replacement therapy with plasma-derived concentrates containing both factor VIII (FVIII) and von Willebrand factor (VWF). Two procedures in patients with acquired von Willebrand syndrome (AWVS) were performed using FVIII-VWF concentrates associated with intravenous immunoglobulins, or desmopressin plus tranexamic acid. Seven procedures were performed using desmopressin alone and one using intravenous immunoglobulins in AVWS. Bleeding complications occurred in seven procedures (22%). In one patient, an anti-VWF antibody was diagnosed after surgery. Anticoagulant prophylaxis of venous thromboembolism was implemented in four cases only and in two instances there was excessive bleeding. In conclusion, control of surgical haemostasis was achieved in most patients with VWD undergoing orthopaedic surgery. The control of haemostasis combined with an adequate surgical technique and early post-operative rehabilitation are warranted for the successful performance of orthopaedic surgery in VWD, which requires the involvement of specialized haemophilia centres.

Management of orthopaedic surgery in rare bleeding disorders.

Knowledge regarding the management of orthopaedic surgery in patients with rare bleeding disorders (RBDs) is limited. Retrospective data collection and analysis of 35 orthopaedic procedures (6 minor and 29 major) carried out in 22 patients with RBD between 1982 and 2013. These surgeries were performed using heterogeneous regimens of hemostatic therapy, except for seven procedures performed with no hemostatic treatment in four patients with mild factor deficiency. Of the 28 procedures carried out with hemostatic treatment, nine (32%) were performed using replacement therapy with dosages of concentrates of the deficient factor aimed to achieve perioperative plasma levels judged to be compatible with hemostasis; three (11%) using factor replacement therapy associated with fresh frozen plasma (FFP); four (14%) using recombinant activated factor VII; four (14%) using virus inactivated plasma alone; three (11%) using virus inactivated plasma associated with desmopressin; one (4%) using FFP alone; and four (14%) procedures using tranexamic acid alone. Bleeding complications occurred in 7 of 35 procedures (20%) involving five patients. Prophylaxis of venous thromboembolism was performed only in one case with no excessive bleeding, but two patients not on thromboprophylaxis developed superficial thrombophlebitis. A satisfactory control of hemostasis was achieved in most patients. In some of those characterized by mild factor deficiency (FVII, FXI) hemostatic treatment could be avoided in some instances. The control of hemostasis combined with an adequate surgical technique is needed for the successful outcome of orthopaedic surgery in RBDs that requires the involvement of specialized haemophilia centres.

Taste responses in sheep medulla: changes during development.

Response characteristics of taste neurons in the sheep solitary tract and nuclei alter during development. Solitary tract cells in younger fetuses respond to stimulation of the tongue with fewer salts and acids than do cells in older fetuses, lambs, and adults. Further, responses to specific salts and acids develop in a particular sequence, not randomly. These changes may relate to maturation of taste receptor sites.

Diagnosis of cardiovascular disease by digital subtraction angiography.

Recent advances in real-time digital video processing have led to a practical method for intravenous arteriography. The digital subtraction technique, which detects small differences in the concentration of the iodinated contrast material injected, is relatively safe and does not usually require hospitalization of the patient. The technique can thus be used for serial evaluation of various clinical problems and for studying the natural history of certain disease processes, as well as for following therapeutic endeavors.

Swallowing in fetal sheep.

Swallowing was measured in fetal sheep by using electromagnetic flowmeter heads chronically implanted in the fetal esophagus. The fetus swallows 20 to 200 milliliters of amniotic fluid in two to seven discrete episodes per day. The episodes are 1 to 9 minutes in duration and occur at seemingly random intervals. Swallowing is influenced by the condition of the fetus and may be the first manifestation of eating and drinking behavior.

Simulation of relative temporal resolution of time-resolved MRA sequences.

Time-resolved MRA sequences are typically characterized by the display frame rate. However, true temporal resolution should be defined in a manner analogous to spatial resolution; it is not the ability of a sequence to update rapidly but rather the ability to discern changes that occur within a small time that should characterize temporal resolution. For view-shared methods like Keyhole and time-resolved imaging of contrast kinetics (TRICKS), regions of k-space from multiple time frames are combined to form a single reconstructed time frame. This often causes the time needed to acquire all k-space data points to be significantly longer than the displayed frame time, resulting in a poor frequency response. Simulated here are the temporal impulse response and temporal frequency response (TFR) curves of three time-resolved MRA methods, including the recently introduced highly-constrained backprojection local reconstruction (HYPR LR) method. It is found that the HYPR LR reconstruction method exhibits a better TFR for a larger spectrum of temporal and spatial frequencies than the Keyhole and TRICKS methods.

Species generalization and differences in Hedgehog pathway regulation of fungiform and circumvallate papilla taste function and somatosensation demonstrated with sonidegib.

Species generalization in the profound, modality-specific effects of Hedgehog pathway inhibition (HPI) in taste organ homeostasis and sensation is shown. With the HPI, cancer drug sonidegib, we demonstrate that the rat taste system, in addition to mouse, is regulated by Hedgehog signaling. After sonidegib treatment for 16-36 days in rat, there is loss of taste buds (TB) in soft palate, in fungiform (FP) and circumvallate papillae (CV), and elimination of taste responses from chorda tympani and glossopharyngeal nerves. The retained innervation in FP and CV during HPI cannot sustain TB. Responses to tactile stimuli are not altered, and temperature responses are reduced only after 28 days treatment, demonstrating modality-specific effects. Rat FP and neural effects are similar to those in mouse whereas TB and neural response effects from the rat CV are much more severe. When recovery is introduced in mouse after prolonged, 48 days HPI, the TB in CV are restored whereas those in FP are not. Overall, Hedgehog signaling regulation is shown to generalize to the rat taste system, and the modality-specific controls in taste organ sensation are affirmed. The reported, debilitating taste disturbances in patients who use HPI drugs can be better understood based on these data.

Quantification of Blood Velocity with 4D Digital Subtraction Angiography Using the Shifted Least-Squares Method.

BACKGROUND AND PURPOSE: 4D-DSA provides time-resolved 3D-DSA volumes with high temporal and spatial resolutions. The purpose of this study is to investigate a shifted least squares method to estimate the blood velocity from the 4D DSA images. Quantitative validation was performed using a flow phantom with an ultrasonic flow probe as ground truth. Quantification of blood velocity in human internal carotid arteries was compared with measurements generated from 3D phase-contrast MR imaging. MATERIALS AND METHODS: The centerlines of selected vascular segments and the time concentration curves of each voxel along the centerlines were determined from the 4D-DSA dataset. The temporal shift required to achieve a minimum difference between any point and other points along the centerline of a segment was calculated. The temporal shift as a function of centerline point position was fit to a straight line to generate the velocity. The proposed shifted least-squares method was first validated using a flow phantom study. Blood velocities were also estimated in the 14 ICAs of human subjects who had both 4D-DSA and phase-contrast MR imaging studies. Linear regression and correlation analysis were performed on both the phantom study and clinical study, respectively. RESULTS: Mean velocities of the flow phantom calculated from 4D-DSA matched very well with ultrasonic flow probe measurements with 11% relative root mean square error. Mean blood velocities of ICAs calculated from 4D-DSA correlated well with phase-contrast MR imaging measurements with Pearson correlation coefficient r = 0.835. CONCLUSIONS: The availability of 4D-DSA provides the opportunity to use the shifted least-squares method to estimate velocity in vessels within a 3D volume.

Physiological, biochemical and molecular responses to water stress and rehydration in Mediterranean adapted tomato landraces.

Mediterranean tomato landraces adapted to arid environments represent an option to counteract drought, and to address the complexity of responses to water deficit and recovery, which is a crucial component of plant adaptation mechanisms. We investigated physiological, biochemical and molecular responses of two Mediterranean tomato landraces, 'Locale di Salina' (Lc) and 'Pizzutello di Sciacca' (Pz) under two dehydration periods and intermediate rehydration in greenhouse pot experiments. Relationship between CO2 assimilation (A) and stomatal conductance under severe water stress (gs  < 0.05 mol·m-2 ·s-1 ) indicated the occurrence of stomatal and non-stomatal limitations of photosynthesis. Gas exchange promptly recovered within 2-3 days of rehydration. ABA and gs showed a strict exponential relationship. Both leaf ABA and proline peaked under severe water stress. Lc showed higher accumulation of ABA and higher induction of the expression of both NCED and P5CS genes than Pz. Poly(ADP-ribose) polymerase increased during imposition of stress, mainly in Lc, and decreased under severe water stress. The two landraces hardly differed in their physiological performance. Under severe water stress, gs showed low sensitivity to ABA, which instead controlled stomatal closure under moderate water stress (gs  > 0.15 mol·m-2 ·s-1 ). The prompt recovery after rehydration of both landraces confirmed their drought-tolerant behaviour. Differences between the two landraces were instead observed at biochemical and molecular levels.

Physiologic and anatomic assessment of a canine carotid artery stenosis model utilizing phase contrast with vastly undersampled isotropic projection imaging.

BACKGROUND AND PURPOSE: Noninvasive assessment of the hemodynamic significance of carotid stenosis is often performed with MR angiography and supplemented with carotid Doppler sonography. Phase contrast with vastly undersampled isotropic projection reconstruction (PC-VIPR), a novel MR imaging technique, accelerates phase-contrast MR flow imaging and provides both images of the vessels and measurements of blood-flow velocities. For this study, we determined the accuracy of PC-VIPR blood-flow velocity measurements to determine pressure gradients across an experimental carotid stenosis. MATERIALS AND METHODS: A focal stenosis was surgically created in each common carotid artery of 6 canines. Digital subtraction angiography (DSA) was performed, and the degree of stenosis was determined using the North American Symptomatic Carotid Endarterectomy Trial methodology. A microcatheter was positioned in the carotid artery proximal and distal to the stenosis, and pressures were measured in the vessel through the catheter. PC-VIPR was then performed on a 1.5T MR imaging scanner with parameters producing 0.8-mm isotropic voxel resolution. From the velocity measurements, pressure gradients were calculated from the Navier-Stokes relationship to compare with the pressures measured by a catheter. RESULTS: Carotid stenoses in the 50%-85% range were produced in the 12 arteries. Pressure gradients across the stenoses ranged from 6 to 26 mm Hg. The pressure gradient calculated from the PC-VIPR data correlated (r = 0.91, P < .0001) with the actual pressure measurements. CONCLUSION: With PC-VIPR, a novel MR imaging technique, the hemodynamic effect of a stenosis on flow and pressure can be evaluated.

Noninvasive measurement of intra-aneurysmal pressure and flow pattern using phase contrast with vastly undersampled isotropic projection imaging.

BACKGROUND AND PURPOSE: Currently, more reliable parameters to predict the risk of aneurysmal rupture are needed. Intra-aneurysmal pressure gradients and flow maps could provide additional information regarding the risk of rupture. Our hypothesis was that phase contrast with vastly undersampled isotropic projection reconstruction (PC-VIPR), a novel 3D MR imaging sequence, could accurately assess intra-aneurysmal pressure gradients in a canine aneurysmal model when compared with invasive measurements. MATERIALS AND METHODS: A total of 13 surgically created aneurysms in 8 canines were included in this study. Pressure measurements were performed in the parent vessel, aneurysm neck, and 5 regions within the aneurysmal sac with a microcatheter. PC-VIPR sequence was used to obtain cardiac-gated velocity measurements in a region covering the entire aneurysm. The velocity and pressure gradient maps derived from the PC-VIPR data were then coregistered with the anatomic DSA images and compared with catheter measurements. RESULTS: In 7 of the bifurcation aneurysms, the velocity flow maps demonstrated a recirculation flow pattern with a small neck-to-dome pressure gradient (mean, +0.5 mm Hg). In 1 bifurcation aneurysm, a flow jet extending from the neck to the dome with significantly greater pressure gradient (+50.2 mm Hg) was observed. All sidewall aneurysms had low flow in the sac with intermediate pressure gradients (mean, +8.3 mm Hg). High statistical correlation existed between PC-VIPR aneurysmal pressures and microcatheter pressure measurements (R = 0.82, P < .01). CONCLUSION: PC-VIPR can provide anatomic as well as noninvasive quantitative and qualitative hemodynamic information in the canine aneurysm model. The PC-VIPR intra-aneurysmal pressure measurements correlated well with catheter measurements.

3D time-resolved contrast-enhanced cerebrovascular MR angiography with subsecond frame update times using radial k-space trajectories and highly constrained projection reconstruction.

HYPR TRICKS is an acquisition method that combines radial k-space trajectories, sampling k-space at different rates (TRICKS), and a new strategy for image reconstruction that uses highly constrained backprojection reconstruction (HYPR). This approach provides 3D time-resolved contrast-enhanced MR angiograms of the cerebral vessels with subsecond frame update times and submillimeter in-plane spatial resolution. Artifacts are suppressed, and signal-to-noise ratio is well maintained, by using HYPR reconstruction.

Developmental neurobiology of salt taste sensation.

A principal process in the homeostatic control of sodium levels is salt intake, and the sense of taste has a primary role in regulating ingestion. Because ingestion of sodium chloride (NaCl) is essential for life, the taste system for salt sensation might be expected to exhibit mature functional characteristics from very early development. However, major changes in gustatory nerve responses to NaCl take place during development. In sheep and rat, the peripheral nerve responses to NaCl are of low magnitude during early development. Progressively, the taste system acquires an increasing proportion of fibers that respond maximally to NaCl. The sodium responsiveness emerges in the context of shifting peripheral innervation patterns and the apparent addition of functional receptor membrane channels sensitive to the sodium transport blocker, amiloride. These developmental processes can be altered by early manipulation of sodium in the diet.

The value of T2 relaxation times to characterize lumbar intervertebral disks: preliminary results.

BACKGROUND AND PURPOSE: The present standard for staging intervertebral disk degeneration is a discrete scale, consisting usually of 5 stages. The purpose of this pilot study was to investigate the use of T2 measurements as a continuous measure of intervertebral disk degeneration. METHODS: We obtained images in 5 volunteers with a 3D fast spin-echo sequence modified for the purpose of calculating T2 relaxation times from multiple echoes in the echo train. Disks were classified on the basis of conventional criteria into one of the 5 stages of disk degeneration. Average T2 values were calculated for stage II, III, and V disks, which were identified in the volunteers. Differences between the disk levels were analyzed with analysis of variance and differences between stages tested with a Student t test with significance set at the 0.01 level. RESULTS: In the 5 volunteers, 20 stage II, 4 stage III, and a single stage V disk were found. Contour plots showed the highest T2 values in the nucleus pulposus near the vertebral endplates and lower T2 values in the intranuclear cleft region and peripheral annulus fibrosus. Average T2 values were significantly lower in the type III and V disks than in the normal disks. CONCLUSIONS: The study suggests that intervertebral disks can be characterized and classified accurately by means of T2 values. More studies are warranted to determine the range of T2 values for normal disks.

Light touch thresholds in diabetic patients.

To determine whether touch acuity is altered in individuals with maturity-onset diabetes, tactile thresholds on the pad of the index finger of 32 diabetic and 27 nondiabetic subjects were compared. A set of modified Von Frey hairs was used to present touch stimuli in a forced-choice tracking procedure that controls for subject response bias. The mean tactile threshold of diabetic patients was significantly higher than that of nondiabetic subjects, although the difference between the two groups is small. Within the diabetic group, decreased tactile acuity was associated with a longer duration of disease diagnosis, presence of insulin therapy, and low-digit temperature. However, reported presence or absence of peripheral sensory symptoms (tingling, numbness, etc.) in diabetic patients did not relate to touch thresholds. The small but significant increase in touch threshold that was observed in diabetic individuals may provide an early indication of sensory neuropathy. Further use of threshold determinations will contribute to our understanding of sensory changes that accompany diabetes.

Predictors of von Willebrand disease diagnosis in individuals with borderline von Willebrand factor plasma levels.

BACKGROUND: In individuals with borderline von Willebrand factor (VWF) plasma levels, second-level tests are required to confirm or exclude von Willebrand disease (VWD). These tests are time-consuming and expensive. OBJECTIVE: To assess which parameters can predict VWD diagnosis in individuals with borderline VWF levels (30-60 IU dL(-1) ). METHODS: Nine hundred and fifty individuals with bleeding episodes or abnormal coagulation test results were investigated with first-level tests (blood count, prothrombin time, activated partial thromboplastin time, blood clotting factor VIII, VWF ristocetin cofactor activity [VWF:RCo], and VWF antigen), and 93 (62 females and 31 males; median age, 28 years; interquartile range 15-44) had borderline VWF:RCo levels. All underwent second-level investigations to confirm or exclude VWD. A multivariable logistic regression model was fitted with sex, age, bleeding score, family history, VWF:RCo and ABO blood group as predictors, and used to predict VWD diagnosis. RESULTS: Forty-five of the 93 individuals (48%) had VWD (84% type 1). A negative linear relationship between VWF:RCo levels and risk of VWD diagnosis was present, and was particularly evident with blood group non-O [adjusted odds ratio 7.00 (95% confidence interval [CI] 1.48-33.11) for every 5 IU dL(-1) decrease in VWF:RCo]. The other variable clearly associated with VWD diagnosis was female sex (adjusted odds ratio 5.76 [95% CI 1.47-22.53]). The area under the receiver operating characteristic curve of the full logistic model was 0.89 (95% CI 0.82-0.95). CONCLUSIONS: In individuals with borderline VWF, the two strongest predictors of VWD diagnosis are low VWF:RCo levels (particularly in those with blood group non-O) and female sex. This predictive model has a promising discriminative ability to identify patients with borderline VWF levels who are likely to have VWD.

Fast contrast-enhanced 4D MRA and 4D flow MRI using constrained reconstruction (HYPRFlow): potential applications for brain arteriovenous malformations.

BACKGROUND AND PURPOSE: HYPRFlow is a novel imaging strategy that provides fast, high-resolution contrast-enhanced time-resolved images and measurement of the velocity of the entire cerebrovascular system. Our hypothesis was that the images obtained with this strategy are of adequate diagnostic image quality to delineate the major components of AVMs. MATERIALS AND METHODS: HYPRFlow and 3D TOF scans were obtained in 21 patients with AVMs with correlative DSA examinations in 14 patients. The examinations were scored for image quality and graded by using the Spetzler-Martin criteria. Mean arterial transit time and overlap integrals were calculated from the dynamic image data. Volume flow rates in normal arteries and AVM feeding arteries were measured from the phase contrast data. RESULTS: HYPRFlow was equivalent to 3D-TOF in delineating normal arterial anatomy, arterial feeders, and nidus size and was concordant with DSA for AVM grading and venous drainage in 13 of the 14 examinations. Mean arterial transit time on the AVM side was 0.49 seconds, and on the normal contralateral side, 2.53 seconds with P < .001. Across all 21 subjects, the mean arterial volume flow rate in the M1 segment ipsilateral to the AVM was 4.07 ± 3.04 mL/s; on the contralateral M1 segment, it was 2.09 ± 0.64 mL/s. The mean volume flow rate in the largest feeding artery to the AVM was 3.86 ± 2.74 mL/s. CONCLUSIONS: HYPRFlow provides an alternative approach to the MRA evaluation of AVMs, with the advantages of increased coverage, 0.75-second temporal resolution, 0.68-mm isotropic spatial resolution, and quantitative measurement of flow in 6 minutes.

Temporal and spatial patterns of tenascin and laminin immunoreactivity suggest roles for extracellular matrix in development of gustatory papillae and taste buds.

Gustatory papillae are complex organs that are composed of 1) an epithelium, 2) specialized sensory cells within the epithelium (the taste buds), 3) a broad connective core, and 4) sensory innervation. During papilla development, cells in the various tissue compartments must divide, aggregate, detach, migrate, and reaggregate in relation to each other, but factors that regulate such steps are poorly understood and have not been extensively studied. All of these processes potentially require participation of the extracellular matrix. Therefore, we have studied temporal and spatial patterns of immunoreactivity for two extracellular matrix molecules, tenascin and laminin, in the developing fungiform and circumvallate papillae of fetal, perinatal, and adult sheep tongue. To determine relations of tenascin and laminin to sensory innervation, we used an antibody to growth-associated protein (GAP-43) to label growing nerves. Immunocytochemical distributions of tenascin and laminin alter during development in a manner that reflects morphogenesis rather than histologic boundaries of the taste papillae. In early fungiform papillae, tenascin immunoreactivity is very weak within the mesenchyme of the papilla core. However, there is a subsequent shift to an intense, restricted localization in the apical papilla core only--directly under taste bud-bearing regions of the papilla epithelium. In early circumvallate papillae, tenascin immunoreactivity is patchy within the papilla core and within the flanking, nongustatory papillae. Later, immunoreactivity is restricted to the perimeter of the central papilla core, under epithelium that contains developing taste buds. In fungiform and circumvallate papillae, the shift in tenascin immunolocalization is associated with periods of taste bud formation and multiplication within the papilla epithelium and with extensive branching of the sensory innervation in the papilla apex. Laminin immunoreactivity, although it is continuous throughout the basement membrane of general lingual epithelium, is interrupted in the epithelial basement membrane of early fungiform and circumvallate papillae in regions where taste buds are forming. The breaks are large in young fetuses, when taste buds first develop, and are evidenced later as punctate disruptions. Heparan sulfate proteoglycan immunoreactivity confirms that these are basement membrane discontinuities. GAP-43 label coincides with innervation of the papilla core and is most extensive in regions where tenascin immunoreactivity is weak or absent. GAP-43 immunoreactivity is also found in early taste buds: Later, it is extensive within more mature multiple taste buds, presumably in relation to synaptogenesis. We propose that tenascin has a role in promoting deadhesion of cells in the papilla epithelium during periods of taste bud formation and multiplication. Discontinuities in the epithelial basement membrane under developing taste buds, indicated with laminin and heparan sulfate proteoglycan immunoreactivity, may interact to facilitate taste bud morphogenesis and multiplication, to permit access of papilla innervation to the forming taste buds, and/or to allow epithelial/mesenchymal interactions during papilla and taste bud development.