The effect of horseshoes and surfaces on horse and jockey centre of mass displacements at gallop

Horseshoes influence how horses' hooves interact with different ground surfaces, during the impact, loading and push-off phases of a stride cycle. Consequently, they impact on the biomechanics of horses' proximal limb segments and upper body. By implication, different shoe and surface combinations could drive changes in the magnitude and stability of movement patterns in horse-jockey dyads. This study aimed to quantify centre of mass (COM) displacements in horse-jockey dyads galloping on turf and artificial tracks in four shoeing conditions: 1) aluminium; 2) barefoot; 3) GluShu; and 4) steel. Thirteen retired racehorses and two jockeys at the British Racing School were recruited for this intervention study. Tri-axial acceleration data were collected close to the COM for the horse (girth) and jockey (kidney-belt), using iPhones (Apple Inc.) equipped with an iOS app (SensorLog, sample rate = 50 Hz). Shoe-surface combinations were tested in a randomized order and horse-jockey pairings remained constant. Tri-axial acceleration data from gallop runs were filtered using bandpass Butterworth filters with cut-off frequencies of 15 Hz and 1 Hz, then integrated for displacement using Matlab. Peak displacement was assessed in both directions (positive 'maxima', negative 'minima') along the cranio-caudal (CC, positive = forwards), medio-lateral (ML, positive = right) and dorso-ventral (DV, positive = up) axes for all strides with frequency ≥2 Hz (mean = 2.06 Hz). Linear mixed-models determined whether surfaces, shoes or shoe-surface interactions (fixed factors) significantly affected the displacement patterns observed, with day, run and horse-jockey pairs included as random factors; significance was set at p<0.05. Data indicated that surface-type significantly affected peak COM displacements in all directions for the horse (p<0.0005) and for all directions (p≤0.008) but forwards in the jockey. The largest differences were observed in the DV-axis, with an additional 5.7 mm and 2.5 mm of downwards displacement for the horse and jockey, respectively, on the artificial surface. Shoeing condition significantly affected all displacement parameters except ML-axis minima for the horse (p≤0.007), and all displacement parameters for the jockey (p<0.0005). Absolute differences were again largest vertically, with notable similarities amongst displacements from barefoot and aluminium trials compared to GluShu and steel. Shoe-surface interactions affected all but CC-axis minima for the jockey (p≤0.002), but only the ML-axis minima and maxima and DV-axis maxima for the horse (p≤0.008). The results support the idea that hoof-surface interface interventions can significantly affect horse and jockey upper-body displacements. Greater sink of hooves on impact, combined with increased push-off during the propulsive phase, could explain the higher vertical displacements on the artificial track. Variations in distal limb mass associated with shoe-type may drive compensatory COM displacements to minimize the energetic cost of movement. The artificial surface and steel shoes provoked the least CC-axis movement of the jockey, so may promote greatest stability. However, differences between horse and jockey mean displacements indicated DV-axis and CC-axis offsets with compensatory increases and decreases, suggesting the dyad might operate within displacement limits to maintain stability. Further work is needed to relate COM displacements to hoof kinematics and to determine whether there is an optimum configuration of COM displacement to optimise performance and minimise injury.

Influence of Speed, Ground Surface and Shoeing Condition on Hoof Breakover Duration in Galloping Thoroughbred Racehorses

Simple Summary

In the stride cycle of a horse, there is a period of time when the hoof pushes off from the ground surface and rotates through an angle of approximately 90 degrees before it is lifted off. This time period is known as hoof breakover. Using slow-motion video footage, this study measured breakover duration in retired Thoroughbred racehorses galloping at a range of speeds on two surfaces (artificial and turf) in four shoeing conditions (aluminium, barefoot, GluShu and steel). Hooves from different limbs were assessed separately in this asymmetric gait. Increasing speed was correlated with decreasing breakover duration, and this trend was more enhanced in the hindlimbs than in the forelimbs at high gallop speeds. Breakover duration was faster on the artificial surface compared to the turf surface for all limbs, under the ground conditions studied. The first limb to contact the ground surface after the suspension phase (the ‘non-leading’ hindlimb), was additionally influenced by shoeing condition and an interaction that occurred between shoeing condition and speed. Determining parameters that alter breakover duration will be important for lowering the risk of musculo-skeletal injuries, optimising gait quality and improving performance in galloping racehorses during both training and racing.

Abstract

Understanding the effect of horseshoe–surface combinations on hoof kinematics at gallop is relevant for optimising performance and minimising injury in racehorse–jockey dyads. This intervention study assessed hoof breakover duration in Thoroughbred ex-racehorses from the British Racing School galloping on turf and artificial tracks in four shoeing conditions: aluminium, barefoot, aluminium–rubber composite (GluShu) and steel. Shoe–surface combinations were tested in a randomized order and horse–jockey pairings (n = 14) remained constant. High-speed video cameras (Sony DSC-RX100M5) filmed the hoof-ground interactions at 1000 frames per second. The time taken for a hoof marker wand fixed to the lateral hoof wall to rotate through an angle of 90 degrees during 384 breakover events was quantified using Tracker software. Data were collected for leading and non-leading forelimbs and hindlimbs, at gallop speeds ranging from 23–56 km h⁻¹. Linear mixed-models assessed whether speed, surface, shoeing condition and any interaction between these parameters (fixed factors) significantly affected breakover duration. Day and horse–jockey pair were included as random factors and speed was included as a covariate. The significance threshold was set at p < 0.05. For all limbs, breakover times decreased as gallop speed increased (p < 0.0005), although a greater relative reduction in breakover duration for hindlimbs was apparent beyond approximately 45 km h⁻¹. Breakover duration was longer on turf compared to the artificial surface (p ≤ 0.04). In the non-leading hindlimb only, breakover duration was affected by shoeing condition (p = 0.025) and an interaction between shoeing condition and speed (p = 0.023). This work demonstrates that speed, ground surface and shoeing condition are important factors influencing the galloping gait of the Thoroughbred racehorse.

Jockey Perception of Shoe and Surface Effects on Hoof-Ground Interactions and Implications for Safety in the Galloping Thoroughbred Racehorse

Riding racehorses is a high-risk profession and optimizing safety alongside performance is paramount. Horseshoes play a critical role in providing traction with the ground surface and are therefore a major determinant of safety. However, the subjective perceptions of expert riders influence attitudes towards using different shoes and must be taken into consideration before any changes may be implemented. This study used a questionnaire-based method to evaluate jockey opinion of four shoeing conditions (aluminum, steel, GluShu, and barefoot) trialed at gallop over turf and artificial surfaces. Nine Lickert-style questions explored impact, cushioning, responsiveness, grip, uniformity, smoothness of ride, safety, adaptation period, and overall rating for each shoe-surface combination. A total of 94 questionnaires, based on 15 horse-rider pairs, were assessed using descriptive statistics and linear mixed models performed in SPSS (P < .05). Data indicate that shoe type significantly affected all question responses, with the exception of impact. Surface-type significantly affected perception of grip and safety. Overall, jockeys showed a preference for aluminum and steel shoes across both artificial and turf tracks. These rated "excellent" and were considered to be "very supportive" in approximately 80% of trials, with a 100% "active" response, good grip, and a quick adaptation period. In contrast, barefoot and GluShu conditions were generally considered "moderately supportive," with barefoot appearing favorable on the artificial surface. On turf, barefoot was deemed the least smooth and the only condition that jockeys sometimes marked "unsafe" (17% of responses). Future work aims to investigate the relationship between jockey opinion and hoof kinematic data.

An in vitro model for the study of taste papillae morphogenesis using branchial arch explants

It is generally accepted that innervation is required for the maintenance of taste papillae and taste buds, but it is not entirely clear what role, if any, innervation plays in papillae and taste bud formation. Events in taste papillae formation and differentiation take place almost entirely in utero and, therefore, the study of the role of innervation in these events requires a suitable in vitro model. In the past, investigators have made use of various culture techniques to study mammalian taste papillae development in vitro and the role of innervation in this process with varying success. All of these models examined papillae development in isolated tongue or tongue fragments and have lacked the ability to manipulate the innervation of developing taste papillae in these explants. We have established a protocol for an in vitro model of taste papillae morphogenesis using branchial arch explants and roller tube culture methodology. Our results demonstrate that this model supports the morphogenesis of the circumvallate papilla with an integrated nerve. In addition, the use of branchial arch explants allows the inclusion or exclusion of geniculate and petrosal ganglia to examine directly the effects of the presence or absence of innervation on papillae formation and maintenance.

The effects of sialoadenectomy and exogenous EGF on taste bud morphology and maintenance

Taste buds on the dorsal tongue surface are continually bathed in saliva rich in epidermal growth factor (EGF). In the following experiment, taste bud number and morphology were monitored following submandibular and sublingual salivary gland removal (sialoadenectomy), to determine if EGF plays a role in the maintenance and formation of taste buds. Adult male rats were divided into four groups: sialoadenectomized (SX, n = 4); sialoadenectomized with EGF replacement (SX + EGF, n = 5); sham-operated (SH, n = 4); and sham-operated with exogenous EGF (SH + EGF, n = 5). After a 3 week recovery, SX + EGF and SH + EGF animals were given 50 microg/day EGF in their drinking water for 14 days. At day 14, saliva was collected, the animals were killed and the presence of EGF determined by radioligand-binding assay. Tongues were removed and histologically examined for the presence and morphology of taste buds on fungiform and circumvallate papillae, or immunostained for the presence of EGF, TGFalpha (transforming growth factor alpha) and EGFR (EGF receptor). The removal of submandibular and sublingual salivary glands resulted in the loss of fungiform taste buds and normal fungiform papillae morphology. These effects were reversed by EGF supplementation, indicating a role for EGF in fungiform taste bud maintenance. In addition, supplementation of EGF to sham-operated animals increased the size of fungiform taste buds. In contrast, removal of salivary glands had no effect on the size, numbers, or morphology of circumvallate taste buds, suggesting that the formation and maintenance of taste buds in fungiform and circumvallate papillae may involve different and distinct processes. EGF, TGFalpha and EGFR were localized to distinct layers of the dorsal epithelium and to within both fungiform and circumvallate taste buds. Their expression within the epithelium or taste buds was not altered with sialoadenectomy, indicating that the actions of endogenous EGF and TGFalpha are distinct and not regulated by exogenous EGF and TGFalpha supplied in saliva.

Occurrence and temporal variation in matrix metalloproteinases and their inhibitors during murine secondary palatal morphogenesis

Extracellular matrix (ECM) molecules are known to play a pivotal role in morphogenesis of the secondary palate, and changes in their composition and distribution, not attributable to changes in synthesis, are known to occur during palatogenesis. The present study was undertaken to determine if the enzymes responsible for mediating their degradation, the matrix metalloproteinases (MMP), and their specific inhibitors, the tissue inhibitors of metalloproteinases (TIMP), are temporospatially regulated during murine palatal shelf morphogenesis. Palatal shelves were harvested at gestational days (gd) 12, 13 and 14. MMPs were identified by gelatin zymography, with and without inhibitors, and the identity of specific bands confirmed by Western blot analysis. TIMPs were identified by reverse zymography. MMP and TIMP messages were detected using RT-PCR with specific primers to MMPs 2, 3, 7, 9 and 13 and TIMPs 1 and 2. Zymography revealed bands of molecular weights corresponding to MMPs 2, 7, 9 and 13 at all ages examined; the intensity of these bands increased with developmental age. Western blot analysis established the presence of MMP-3 and its developmental variation in expression. RT-PCR demonstrated the presence of mRNA for all MMPs and TIMP at all sampling times and all but MMP-2 showed developmental variation. Whereas increases in mRNA were detected for MMPs 3, 9, and 13, MMP-7 mRNA decreased between gd 12 and 14. The results of this study demonstrate that MMPs 2, 3, 7, 9 and 13 and TIMPs 1 and 2 and their messages are present during the course of palatal shelf remodelling and that their expression is temporally regulated.

An in vitro model for the study of the role of innervation in circumvallate papillae morphogenesis

The following study was done to demonstrate the reliability of an in vitro model for use in the study of early events and the role of innervation in mouse circumvallate papillae development. Gestational day (gd)-11 fetuses were partially dissected to produce explants that included the mandibular, hyoid, third and fourth branchial arches and their ganglia. In ganglionectomized explants, the nodose ganglia and either the geniculate, petrosal or both ganglia were removed. Explants were cultivated in roller tube culture for 24, 48, 72, and 96 h of culture and examined for the presence of papillary structures. Innervation was verified by immunostaining for neural cell adhesion molecule (NCAM). In all control explants, circumvallate papillae had formed by 72 h in culture. These papillae were innervated by fibers originating in petrosal or nodose ganglia, although, in a small number, fibers from the geniculate also contributed. Circumvallate papillae also formed in some explants in which either the geniculate or petrosal ganglia had been removed. However, placodal structures failed to mature into papillary structures even by 96 h in explants in which both ganglia had been removed. Our results demonstrate that an in vitro model using branchial arch explants supports the morphogenesis of an epithelial placode through the formation of a definite papillary structure, the circumvallate papilla, with an integrated nerve. Our results also indicate that, whereas the initial stages in gustatory papillae formation, the formation of a placode, are nerve-independent, the maturation of the placodal structure to form a papilla requires the presence of an intact nerve.

Effects of a large supper on glucose levels the following morning in patients with type 2 diabetes

Seventeen patients were studied to test the hypothesis that a large evening meal influences the fasting glucose level and glucose tolerance the following morning in patients with type 2 diabetes. Oral hypoglycemic agents were discontinued for 2 weeks. The baseline fasting plasma glucose levels were 12.3 +/- 0.9 mmol/L. Fasting and postprandial (post-Sustacal) glucose, insulin, and C-peptide measurements were performed the morning after the patients received three separate meal protocols spaced 1 week apart. The caloric distribution of the meal protocols was (1) 7 kcal/kg of ideal body weight breakfast and lunch and 14 kcal/kg supper (small supper); (2) 7 kcal/kg breakfast and lunch and 28 kcal/kg for supper (large supper); and (3) 14 kcal/kg breakfast and lunch (no supper). Fasting glucose level were higher the morning after the large supper compared to no supper (13.6 +/- 0.7 versus 12.3 +/- 0.5 mmol/L, p < 0.05) and also to the small supper (13.6 +/- 0.7 versus 12.5 +/- 0.6 mmol/L, p = 0.05). No difference was observed in the fasting glucose levels between the small supper and no supper (p > 0.2). The fasting insulin and C-peptide levels, and the post-Sustacal areas under the curve of glucose, insulin, and C-peptide did not differ among the meals. In patients with type 2 diabetes, a large evening meal is associated with a modest elevation in fasting glucose the following morning.

Effects of varying carbohydrate content of diet in patients with non-insulin-dependent diabetes mellitus

OBJECTIVE

To study effects of variation in carbohydrate content of diet on glycemia and plasma lipoproteins in patients with non-insulin-dependent diabetes mellitus (NIDDM).

DESIGN

A four-center randomized crossover trial.

SETTING

Outpatient and inpatient evaluation in metabolic units.

PATIENTS

Forty-two NIDDM patients receiving glipizide therapy.

INTERVENTIONS

A high-carbohydrate diet containing 55% of the total energy as carbohydrates and 30% as fats was compared with a high-monounsaturated-fat diet containing 40% carbohydrates and 45% fats. The amounts of saturated fats, polyunsaturated fats, cholesterol, sucrose, and protein were similar. The study diets, prepared in metabolic kitchens, were provided as the sole nutrients to subjects for 6 weeks each. To assess longer-term effects, a subgroup of 21 patients continued the diet they received second for an additional 8 weeks.

MAIN OUTCOME MEASURES

Fasting plasma glucose, insulin, lipoproteins, and glycosylated hemoglobin concentrations. Twenty-four-hour profiles of glucose, insulin, and triglyceride levels.

RESULTS

The site of study as well as the diet order did not affect the results. Compared with the high-monounsaturated-fat diet, the high-carbohydrate diet increased fasting plasma triglyceride levels and very low-density lipoprotein cholesterol levels by 24% (P < .0001) and 23% (P = .0001), respectively, and increased daylong plasma triglyceride, glucose, and insulin values by 10% (P = .03), 12% (P < .0001), and 9% (P = .02), respectively. Plasma total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol levels remained unchanged. The effects of both diets on plasma glucose, insulin, and triglyceride levels persisted for 14 weeks.

CONCLUSIONS

In NIDDM patients, high-carbohydrate diets compared with high-monounsaturated-fat diets caused persistent deterioration of glycemic control and accentuation of hyperinsulinemia, as well as increased plasma triglyceride and very-low-density lipoprotein cholesterol levels, which may not be desirable.

Effects of sialoadenectomy and exogenous EGF on molar drift and orthodontic tooth movement in rats

Effects on bone remodeling have been attributed to epidermal growth factor (EGF). Sialoadenectomy (SX) removes the major source of EGF in rodents and decreases both salivary and serum EGF levels. EGF effects on rat alveolar bone remodeling manifested by molar drift (MD) and orthodontic tooth movement (OTM) were examined using the following two approaches: 1) EGF depletion by SX and replacement by orally administered EGF (50 micrograms.animal-1.day-1); 2) sham rats supplemented with matching amounts of EGF. MD and OTM were measured using cephalometric radiographs; bone formation was measured histomorphometrically using tetracycline labeling. Normal MD was not detected after SX, and alveolar bone formation was significantly reduced both around the tooth and in nondental sites. Replacement EGF given to SX rats and supplemental EGF administered to sham rats changed the direction and enhanced the rate of MD. A mesially directed orthodontic force applied to the molars of SX animals increased bone formation on the distal aspect of the tooth roots. Supplemental EGF did not significantly affect OTM. EGF affects alveolar bone remodeling, as manifested clinically by alterations in normal maxillary MD.

Characterization of antinuclear autoantibodies present in the serum from nonobese diabetic (NOD) mice

The nonobese diabetic (NOD) mouse develops insulin-dependent type 1 diabetes in response to autoantibodies and T-cell attack directed against pancreatic islet cell antigens. Sera obtained from nondiabetic and diabetic female mice demonstrated a 1.4-fold increase in IgG levels when compared to BALB/c control animals. Nondiabetic and diabetic male mice had a 2.1- and 3-fold increase, respectively, in serum IgG levels over that of control mice. Seven of 11 non-diabetic and 7/10 diabetic sera from female NOD mice contained antibody to cytoplasmic or nuclear components of HEp-2 cells. Cytoplasmic staining revealed reaction against cytoskeletal and midbody structures. Punctate nuclear staining patterns with HEp-2 cells showed antibody reaction to the centriole, mitotic chromosomes, and nuclear rim. On the other hand, sera from BALB/c mice were negative for antibody staining of HEp-2 cells. Confirmation of the autoantibody nature of the NOD sera was obtained by antibody staining of nuclear structures from the mouse 3T3 fibroblast cell line, and by staining of salivary gland tissue sections. The nuclear and cytoplasmic staining patterns of diabetic NOD sera were reminiscent of the autoantibody staining patterns observed in Sjögren's syndrome and other inflammatory autoimmune connective tissue diseases.

Rapid changes in the extracellular matrix accompany in vitro palatal shelf remodelling

The sequence of events and the distribution of extracellular matrix (ECM) components was examined during mouse secondary palatal shelf elevation in an in vitro model using standard roller tube culture methods developed for the culture of early embryos. In this culture system, the morphological changes associated with remodelling and reorientation of the palatal shelves of gestational day 13 mouse fetuses were similar to those observed in vivo. However, in specimens explanted 24-30 h prior to reorientation in vivo, remodelling began rapidly after explantation, and significant reorientation was accomplished within 4 h. Midline contact between the shelves did not occur until after 18 h in vitro, concomitant with shelf growth. Therefore, in this in vitro model, events related to palatal shelf remodelling and reorientation can be distinguished from those related to shelf growth. We used this in vitro model to characterize the transient changes in ECM distribution and accumulation that occur concomitant with events in shelf remodelling. Our results show that, during rapid remodelling in vitro, the relative distributions of collagen III, fibronectin and hyaluronate, as visualized by immunofluorescent staining, decreased within specific regions of the mesenchymal compartment. In contrast, the distribution of collagen I within the mesenchyme increased, and the distribution of tenascin did not change significantly. All molecules examined, except tenascin, showed changes in distribution within the basement membrane. These patterns of distribution are similar to those observed during more gradual remodelling in vivo. During remodelling in vitro, the deposition of [3H]-glucosamine- and [3H]-proline-labelled components of the ECM, as visualized by autoradiography, was greatest during the first 3 h of culture. During this period, labelled ECM accumulated within specific regions of the mesenchyme and palatal epithelial basement membrane. Uptake was reduced dramatically during the subsequent 3 h in culture and was restricted mainly to the palatal epithelium and its underlying basement membrane. The in vitro system permitted the characterization of early events in shelf remodelling leading to reorientation. Results suggest that remodelling is accompanied by rapid, local accumulation of ECM in specific regions of the palatal shelf previously thought to play a role in the process.

An extracellular matrix infrastructure provides support for murine secondary palatal shelf remodelling

A crucial part of secondary palate morphogenesis is the movement of the palatal shelves from an initial vertical position on either side of the tongue to a final horizontal one above it to achieve palate closure. The immunocytochemical localization of extracellular matrix (ECM) molecules in the palatal shelf during this remodelling and reorientation revealed the existence of an ECM infrastructure within the mesenchyme. The major components of this infrastructure were collagen III, fibronectin, and hyaluronate (HA). With remodelling, HA's domain within the mesenchyme was expanded, whereas those of fibronectin and collagen III became more circumscribed. The expansion of an HA-rich matrix within the mesenchyme is thought to be crucial for palatal reorientation. The results of this study suggest that, as this expansion occurs, it is modulated by collagen and fibronectin components of the ECM infrastructure. Prior to shelf remodelling, this infrastructure may be anchored by a specialized region of the midoral epithelial-mesenchymal interface and the subjacent mesenchyme which is characterized by the unique distribution of collagen III, fibronectin, and tenascin. The midoral palatal epithelium also may play a role in directing shelf expansion. This epithelial region undergoes changes in cell packing and epithelial cell layering that correlate with shelf remodelling. These changes occur concomitantly with changes in the expression of collagen III, collagen IV, and laminin within the underlying basement membrane. The localization and patterning of tenascin within the developing palate suggests that it not only contributes to the postulated anchoring structure of the midoral epithelial-mesenchymal region, but also plays a role in the determining the fate of the medial edge epithelial cells during the final stage of palate closure.

The distribution of syndecan during murine secondary palate morphogenesis

The distribution of syndecan, an integral membrane proteoglycan, has been immunohistochemically mapped during the course of murine secondary palate morphogenesis, gestational days 12-15. Syndecan has been shown to mediate cell adhesion and shape change and to be involved in epithelial-mesenchymal interactions during the morphogenesis of several structures. Changes in epithelial cell architecture accompany and may serve to direct the reorientation of the murine secondary palatal shelves from a vertical position on either side of the tongue to a horizontal and adhering position above it. Using a monoclonal antibody made to the core protein of the ectodomain of syndecan, staining was observed to correlate with epithelial cell shape, packing and degree of differentiation. Staining of condensing mesenchyme was also observed. Syndecan may be involved in modulating epithelial cell shape, architecture and fates during both major phases of secondary palate morphogenesis: shelf reorientation and midline epithelial seam dissolution.

Relationship of animal protein-rich diet to kidney stone formation and calcium metabolism

We wished to determine whether different types of dietary protein might have different effects on calcium metabolism and on the propensity for renal stone formation. Fifteen young normal subjects were studied during three 12-day dietary periods during which their diet contained vegetable protein, vegetable and egg protein, or animal protein. While these three diets were constant with respect to Na, K, Ca, P, Mg, and quantity of protein, they had progressively higher sulfur contents. As the fixed acid content of the diets increased, urinary calcium excretion increased from 103 +/- 15 ( +/- SEM) mg/day (2.6 +/- 0.4 mmol/day) on the vegetarian diet to 150 +/- 13 mg/day (3.7 +/- 0.3 mmol/day) on the animal protein diet (P less than 0.02). Despite the increased urinary calcium excretion, there was a modest reduction of urinary cAMP excretion and serum PTH and 1,25-dihydroxyvitamin D levels consistent with acid-induced bone dissolution. There was no change in fractional intestinal 47Ca absorption. The inability to compensate for the animal protein-induced calciuric response may be a risk factor for the development of osteoporosis. The animal protein-rich diet was associated with the highest excretion of undissociated uric acid due to the reduction in urinary pH. Moreover, citrate excretion was reduced because of the acid load. However, oxalate excretion was lower than during the vegetarian diet [26 +/- 1 mg/day (290 +/- 10 mumol/day) vs. 39 +/- 2 mg/day (430 +/- 20 mumol/day); P less than 0.02]. Urinary crystallization studies revealed that the animal protein diet, when its electrolyte composition and quantity of protein were kept the same as for the vegetarian diet, conferred an increased risk for uric acid stones, but, because of opposing factors, not for calcium oxalate or calcium phosphate stones.

Augmentation of renal citrate excretion by oral potassium citrate administration: time course, dose frequency schedule, and dose-response relationship

The time course, dose frequency schedule, and dose-response relationship of the citraturic response to orally administered potassium citrate was examined in 22 normal volunteers and 21 patients with uric acid or calcium nephrolithiasis. The slow-release (wax matrix) preparation of potassium citrate produced a rapid and sustained rise in urinary citrate lasting for up to 12 hours following a single oral administration. Probably owing to this prolonged action, the slow-release preparation when given in a twice-daily or thrice-daily schedule at a dosage of 60 meq or 3.78 Gm citrate/day virtually eliminated the normally wide circadian fluctuation in urinary citrate and maintained urinary citrate at a higher, more constant level throughout the day. The liquid preparation of potassium citrate was less effective in this regard. However, the two preparations of potassium citrate caused an equivalent rise in total 24-hour urinary citrate. When 24-hour excretions of citrate were examined, urinary citrate was shown to reach its peak level by the second day of potassium citrate treatment and to return to the pretreatment level by the second day after the treatment was stopped. The rise in urinary citrate produced by treatment was directly proportional to the dose of potassium citrate. In most hypocitraturic patients with renal stones, potassium citrate 60 meq/day restored normal urinary citrate (greater than 320 mg/day).

Bioavailability of oxalate in foods

The ability of 7 "oxalate-rich" foods to enhance urinary oxalate excretion was measured in 8 normal volunteers. The analyzed value for oxalate was high for spinach (1,236 mg.), moderate for chocolate (126 mg.) and tea (66 mg.), and for low vegetable juice, cranberry juice, pecans, and orange juice (2 to 26 mg.). The urinary oxalate increased by 29.3 mg. during eight hours after ingestion of spinach. However, it rose by less than 4.2 mg. from consumption of other food items. The bioavailable oxalate (per cent of total appearing in urine) was much less from food items of high or moderate oxalate content (spinach and chocolate) than from standard solutions of sodium oxalate (2.4 to 2.6 versus 6.5 to 7.3 per cent). Thus, only spinach among food items tested was capable of causing hyperoxaluria in normal subjects.

Evidence justifying a high fluid intake in treatment of nephrolithiasis

We quantitatively assessed the effect of urinary dilution on the crystallization of calcium salts. Urinary dilution was achieved in vitro (1 to 2 L/d) by addition of water to urine from six patients with renal stones and two normal subjects, and in vivo (1.023 to 2.383 L/d) by an increased ingestion of distilled water in four patients with nephrolithiasis and three normal subjects. Both forms of urinary dilution significantly reduced the urinary activity product ratio (state of saturation) of calcium phosphate (brushite), calcium oxalate, and monosodium urate. Moreover, the formation product ratio (limit of metastability or minimum supersaturation needed to elicit spontaneous nucleation) of calcium oxalate significantly increased, although that for brushite did not change significantly. Thus, there was a reduced propensity for crystallization of calcium salts. The results provide objective evidence for the beneficial role of an increased fluid intake in the management of nephrolithiasis.

Effects of craniofacial structures on mouse palatal closure in vitro

Heads of Swiss-Webster mouse fetuses of four ages spanning days 12-13 of gestation, were partially dissected by removing the brain (B), tongue (T) and mandible (M) alone or in combination (BT, BM, BTM). Preparations were suspended in a gassed, circulating culture system such that palatal closure must take place against gravity. Closure occurred earlier than in vivo and required the posterior half of the mandible be intact and the tongue removed.

A new in vitro system for studying secondary palate development

An in vitro system was devised which supports palate development in partially dissected embryonic mouse heads. The heads were suspended in the culture chamber so that they were not held in a fixed orientation and were constantly surrounded with a fluid medium. Under these circumstances the developing palate must effect closure without the aid of gravitational forces. The culture medium was constantly circulated, gassed with 95% O2, 5% CO2 using hollow fiber gas permeation devices, and kept at 34 degrees C. Swiss-Webster mouse embryos of 12 days 12-18 h (ca. 48 h prior to expected in vivo closure) or 13 days 8-14 h (ca. 24 h prior to closure) were used to test the ability of the system to support palatal development. Embryonic heads were dissected in one of two ways before culture: brain and tongue removed, or brain, tongue and mandible removed. After 24 h in culture, preparations of either age with only the brain and tongue removed had made substantially greater progress than their counterparts with the brain, tongue and mandible removed. With only the brain and tongue removed, the palatal shelves were contacting, adhered or fused in 67% of the older embryos of the same age cultured with the brain, tongue and mandible removed had shelves that were not fully elevated and still separated by a moderate gap. Thus for maximal progress in the present system, the oral cavity must be intact except for the tongue.

A new in vitro system for studying secondary palate development

An in vitro system was devised which supports palate development in partially dissected embryonic mouse heads. The heads were suspended in the culture chamber so that they were not held in a fixed orientation and were constantly surrounded with a fluid medium. Under these circumstances the developing palate must effect closure without the aid of gravitational forces. The culture medium was constantly circulated, gassed with 95% O2, 5% CO2 using hollow fiber gas permeation devices, and kept at 34°C. Swiss-Webster mouse embryos of 12 days 12–18 h (ca. 48 h prior to expected in vivo closure) or 13 days 8–14 h (ca. 24 h prior to closure) were used to test the ability of the system to support palatal development. Embryonic heads were dissected in one of two ways before culture: brain and tongue removed, or brain, tongue and mandible removed. After 24 h in culture, preparations of either age with only the brain and tongue removed had made substantially greater progress than their counterparts with the brain, tongue and mandible removed. With only the brain and tongue removed, the palatal shelves were contacting, adhered or fused in 67 % of the older embryos, whereas most of the embryos of the same age cultured with the brain, tongue and mandible removed had shelves that were not fully elevated and still separated by a moderate gap. Thus for maximal progress in the present system, the oral cavity must be intact except for the tongue.