The biomechanical consequences of longirostry in crocodilians and odontocetes.

Unrelated clades of aquatic tetrapod have evolved a similar range of skull shapes, varying from longirostrine (elongate and narrow rostrum) to brevirostrine (short rostrum). However, it is unclear which aspects of organismal performance are associated with this convergence in the range of skull shapes. Furthermore, it is not known how fundamental anatomical differences between groups influence these relationships. Here we address this by examining the load bearing capabilities of the skulls of two of the most diverse groups of living aquatic tetrapod: crocodilians and odontocetes. We use finite element analysis to examine the abilities of different cranial morphologies to resist a range of biologically relevant feeding loads including biting, shaking and twisting. The results allow for form/function relationships to be compared and contrasted between the two groups. We find that cranial shape has similar influences on performance during biting, shaking or twisting load cases at the anterior tooth positions, e.g. brevirostrine species experienced less strain than longirostrine species. The pattern of this form/function relationship is similar for both crocodilians and odontocetes, despite their fundamentally different anatomies. However, when loading teeth at the posterior end or middle of the tooth row the results do not follow the same pattern. Behavioural differences in bite location plays a key role in determining functional abilities in aquatic tetrapod taxa.

Constructing an Invasion Machine: The Rapid Evolution of a Dispersal-Enhancing Phenotype During the Cane Toad Invasion of Australia.

Biological invasions can induce rapid evolutionary change. As cane toads (Rhinella marina) have spread across tropical Australia over an 80-year period, their rate of invasion has increased from around 15 to 60 km per annum. Toads at the invasion front disperse much faster and further than conspecifics from range-core areas, and their offspring inherit that rapid dispersal rate. We investigated morphological changes that have accompanied this dramatic acceleration, by conducting three-dimensional morphometric analyses of toads from both range-core and invasion-front populations. Morphology of heads, limbs, pectoral girdles and pelvic girdles differed significantly between toads from the two areas, ranging from 0.5% to 16.5% difference in mean bone dimensions between populations, with invasion-front toads exhibiting wider forelimbs, narrower hindlimbs and more compact skulls. Those changes plausibly reflect an increased reliance on bounding (multiple short hops in quick succession) rather than separate large leaps. Within an 80-year period, invasive cane toads have converted the basic anuran body plan - which evolved for occasional large leaps to evade predators - into a morphotype better-suited to sustained long-distance travel.

Mechanics of biting in great white and sandtiger sharks.

Although a strong correlation between jaw mechanics and prey selection has been demonstrated in bony fishes (Osteichthyes), how jaw mechanics influence feeding performance in cartilaginous fishes (Chondrichthyes) remains unknown. Hence, tooth shape has been regarded as a primary predictor of feeding behavior in sharks. Here we apply Finite Element Analysis (FEA) to examine form and function in the jaws of two threatened shark species, the great white (Carcharodon carcharias) and the sandtiger (Carcharias taurus). These species possess characteristic tooth shapes believed to reflect dietary preferences. We show that the jaws of sandtigers and great whites are adapted for rapid closure and generation of maximum bite force, respectively, and that these functional differences are consistent with diet and dentition. Our results suggest that in both taxa, insertion of jaw adductor muscles on a central tendon functions to straighten and sustain muscle fibers to nearly orthogonal insertion angles as the mouth opens. We argue that this jaw muscle arrangement allows high bite forces to be maintained across a wider range of gape angles than observed in mammalian models. Finally, our data suggest that the jaws of sub-adult great whites are mechanically vulnerable when handling large prey. In addition to ontogenetic changes in dentition, further mineralization of the jaws may be required to effectively feed on marine mammals. Our study is the first comparative FEA of the jaws for any fish species. Results highlight the potential of FEA for testing previously intractable questions regarding feeding mechanisms in sharks and other vertebrates.

Difficult problems in thyroid cancer surgery.

The incidence of thyroid cancer has increased dramatically, yet the mortality has remained unchanged. There remain many challenges and "difficult problems" in diagnosing and treating patients with differentiated thyroid cancer (DTC). A significant percentage of patients with DTC will present with a thyroid nodule and an indeterminate fine needle aspiration biopsy underscoring the importance of proper evaluation and management. It is important when considering the extent of thyroidectomy and the management of lymph node metastases to balance the outcome of treatment in terms of recurrence and mortality with the morbidity of the procedure. Total thyroidectomy and lymphadenectomy for macroscopic lymph node metastases appear to be the optimal therapy for most patients with DTC. Preservation of function is a priority in managing patients with DTC invading the recurrent laryngeal nerve, trachea, esophagus, or the larynx.

An investigation of epidemiologic factors associated with large nodular goiter.

BACKGROUND: Sporadic nodular goiter is a common problem in the United States and significant compressive symptoms may occur with progression to a critical size. METHODS: Potential epidemiological variables associated with the development of large unilateral (> or = 50 g) and bilateral (> or = 100 g) nodular goiter were investigated including: age, gender, race, body mass index (BMI), family history of thyroid disease, pregnancy at time of diagnosis, insurance status, and tobacco or alcohol use. Data were obtained from an IRB-approved thyroid database and retrospective chart review of consecutive patients operated on for nodular goiter from 1990 through 2005. A univariate and multivariate analysis of epidemiological variables in patients with "large" versus "small" nodular goiter was completed. RESULTS: Of the 488 patients operated on for nodular goiter, 113 (23%) were classified as "large," 43 with unilateral (mean 106 +/- 72 g) and 70 with bilateral enlargement (mean 173 +/- 92 g) and 375 (77%) were classified as "small," 179 with unilateral (18 +/- 10 g) and 196 with bilateral (37 +/- 24 g) enlargement. Based on univariate analysis, African-American race, age > or = 40 years, BMI > or = 30 kg/m2, and lack of insurance were associated with an increased risk of large nodular goiter (P < or = 0.001), whereas alcohol use was protective (P = 0.002). A multivariate analysis revealed that African-American race [adjusted odds ratio (adj. OR) 3.3, 95% CI = 2.0-5.4], age > or = 40 years (adj. OR 2.1, 95% CI = 1.2-3.8), and BMI > or = 30 kg/m2 (adj. OR 2.5, 95% CI = 1.5-4.0) were independently associated with large nodular goiter. No significant differences were observed in gender, family history of thyroid disease, pregnancy, or tobacco use (P > 0.1). CONCLUSIONS: African-American race, obesity, and increasing age are independent risk factors for the development of large nodular goiter. These results may be helpful in determining how best to monitor patients with nodular goiter, with earlier intervention to help prevent progressive enlargement and its sequelae.

Thrombocytopenia caused by splenic hamartoma: resolution after splenectomy.

We report a rare case of isolated thrombocytopenia due to a large hamartoma of the pulposal type, which resolved with splenectomy in a 46-year-old man. Although hamartomas are usually found incidentally, they may cause hematologic disturbances such as thrombocytopenia, anemia, or splenic rupture. The diagnosis of splenic hamartoma is difficult to make preoperatively. Splenectomy is important in excluding malignant tumors from the diagnosis when the etiology of a splenic mass is unclear and ameliorating hematologic symptoms related to hamartomas.

Refractory renal hyperparathyroidism: clinical features and outcome of surgical therapy.

Despite improvements in medical management parathyroidectomy has an important role in treatment of refractory renal hyperparathyroidism (HPT). The medical records of all patients who underwent parathyroidectomy from 1991 through 2000 were reviewed to determine the clinical and laboratory features and outcomes of treatment in patients with renal versus primary HPT. Twenty-one of 92 patients who underwent parathyroidectomy had renal HPT with a mean age of 47+/-3 years compared with 56+/-2 years for patients with primary HPT (P < 0.05). Clinical manifestations included osteodystrophy (19), pruritus (six), extraosseous calcification (three), and calciphylaxis (one). Parathyroid hormone, phosphorus, and alkaline phosphatase levels and weights of excised glands were higher in renal versus primary HPT (P < 0.05). Supernumerary glands were found in three patients (14%) with renal HPT and none of nine patients with primary parathyroid hyperplasia. After surgical therapy persistent or recurrent HPT occurred in three (14%) patients with renal and one (1.4%) patient with primary HPT (P < 0.05). Postoperative hypocalcemia occurred in 20 (95%) patients with renal HPT all of whom required intravenous calcium, compared with 25 (35%) patients with primary HPT (P < 0.05) of whom only three (4%) required intravenous calcium (P < 0.05). In contrast to those with primary HPT patients with renal HPT are younger and more likely to have severe osteodystrophy, postoperative hypocalcemia, and persistent or recurrent HPT.

Thyroidectomy for selected patients with thyrotoxicosis.

OBJECTIVE: To examine the indications for operation and the frequency, efficacy, and outcome of surgical therapy for thyrotoxicosis. METHODS: The medical records of all patients who underwent thyroidectomy between 1990 and 1998 were reviewed. Operative indications, laboratory evaluations, extent of thyroidectomy, pathologic findings, and morbidity and mortality were determined for patients with thyrotoxicosis. RESULTS: Of the 347 patients who underwent thyroidectomy, 54 (16%) had thyrotoxicosis, secondary to Graves' disease (32 patients), toxic multinodular goiter (18 patients), thyroiditis (2 patients), or amiodarone (2 patients). The indications for operation were compressive symptoms or substernal extension or both (35 patients), patient preference (12 patients), thyrotoxicosis (4 patients), or a dominant nodule (3 patients). Most patients received pharmacological preparation, followed by total (32 patients), near-total (13 patients), subtotal (8 patients), or unilateral (1 patient) thyroidectomy. The initial 8 patients with Graves' disease underwent subtotal thyroidectomy, and after a mean 28-month follow-up, 1 was euthyroid; 2, hyperthyroid; and 5, hypothyroid. Associated carcinoma was present in 4 (7%) of the 54 patients. Symptomatic hypocalcemia occurred in 10 patients (19%), with a mean free thyroxine level of 60.49 +/- 16.09 pmol/L vs 40.41 +/- 19.56 pmol/L (4.70 +/- 1.25 ng/dL vs 3.14 +/- 1.52 ng/dL) in 25 patients (46%) with asymptomatic hypocalcemia (P<.05). Vocal cord paresis and a hematoma requiring operative evacuation occurred in 1 patient each. There was 1 mortality in a patient with amiodarone-induced thyrotoxicosis. CONCLUSIONS: Massive thyroid enlargement with compressive symptoms, a dominant nodule, and patient preference are indications for surgical treatment of thyrotoxicosis. Near-total or total thyroidectomy is safe and more effective than subtotal thyroidectomy in preventing recurrence and should be considered in most patients referred for surgical treatment of thyrotoxicosis. Transient postoperative hypocalcemia is common and is related to the severity of thyrotoxicosis.

Hypothyroidisim following hemithyroidectomy: incidence, risk factors, and management.

BACKGROUND: The purpose of this study was to characterize the hypothyroidism that occurs following hemithyroidectomy. METHODS: The records of all euthyroid patients who underwent hemithyroidectomy from 1992 to 2000 were reviewed to determine the frequency of postsurgical hypothyroidism and the predisposing factors. All patients were evaluated for age, gender, serum thyrotropin (TSH) levels, weight of resected thyroid tissue, and associated thyroiditis. Hypothyroid patients were evaluated for symptoms, timing of diagnosis, and treatment doses of levothyroxine (L-T(4)). RESULTS: Hypothyroidism was diagnosed in 25 (35%) of 71 patients, subclinical in 16 and overt in 9 with a mean postoperative TSH level of 8.51 +/- 6.53 microIU/L. The mean preoperative TSH level was 1.94 +/- 1.00 microIU/L in hypothyroid compared with 1.10 +/- 0.74 microIU/L in euthyroid patients (P <.05). Lymphocytic thyroiditis was present in 10 (40%) of 25 hypothyroid compared with 10 (22%) of 46 euthyroid patients (P = not significant). There were no significant differences in age, gender, or weight of resected thyroid tissue. The average therapeutic dose of L-T(4) was 1.3 microg/kg (range, 0.5 to 1.9 microg/kg). All but 2 hypothyroid patients were diagnosed within 2 months of operation. CONCLUSIONS: Hypothyroidism following hemithyroidectomy occurs in patients with higher preoperative TSH levels, is usually mild and asymptomatic, and can be treated with reduced doses of L-T(4).

Recommendations for management of cystic thyroid disease.

BACKGROUND: Thyroidectomy has been advocated for cystic nodules that recur after 2 fine-needle aspiration biopsies (FNABs) because of concern for malignancy. METHODS: A review of patients with nodular thyroid disease was completed to determine the frequency of cystic nodules, significance of the color and volume of aspirated fluid, frequency and factors predictive of cyst resolution, and incidence of carcinoma in cystic nodules. RESULTS: Thyroid nodules were cystic in 70 (18%) of 389 patients. FNAB was diagnostic in 50 (71%) patients with no false-negative results. Cyst resolution occurred in 10 (14%) patients. The mean volume of fluid aspirated from cysts that resolved was 14 +/- 12 mL compared with 8 +/- 18 mL from recurrent cysts (P > .05). Thyroidectomy was performed in 28 (40%) patients because of an abnormal or persistently nondiagnostic FNAB or compressive symptoms. Six patients (8.6%) had cancer, with a mean nodule size of 3.8 +/- 2.3 cm compared with 3.7 +/- 2.6 cm in patients with benign cysts (P > .05). Hemorrhagic fluid was aspirated in 4 patients with and 36 without cancer (P > .05). CONCLUSIONS: FNAB of cystic thyroid nodules is rarely therapeutic and is a common cause of nondiagnostic rather than false-negative results. Recommendations for thyroidectomy should be based on FNAB rather than on size, fluid color, or failure of cyst resolution alone.

Follicular or Hürthle cell neoplasm of the thyroid: can clinical factors be used to predict carcinoma and determine extent of thyroidectomy?

BACKGROUND: Fine-needle aspiration biopsy (FNAB) and frozen section exam are of limited or no value in distinguishing benign and malignant follicular or Hürthle cell neoplasms of the thyroid gland. METHODS: Patients who underwent thyroidectomy for treatment of a follicular or Hürthle cell neoplasm between 1990 and 1998 were identified and evaluated for age, gender, head and neck irradiation, nodule size, and cytologic atypia to determine whether clinical factors were predictive of carcinoma. RESULTS: Of the 352 patients evaluated for nodular thyroid disease, 75 (21%) underwent thyroidectomy after an indeterminate FNAB finding, 66 with follicular and 9 with a Hürthle cell neoplasm. Seventeen (23%) of the patients had carcinoma-follicular variant of papillary (10), follicular (6), and Hürthle cell (1). Carcinoma was diagnosed in 15 of 64 women and 2 of 11 men (P > .05). The mean age was 43 +/- 21 years and 50 +/- 16 years, respectively, in patients with and without carcinoma (P > . 05). Three patients had previous neck irradiation and none had carcinoma. Mean nodule size was 4.2 +/- 2.7 cm and 4.3 +/- 3.5 cm, respectively, in patients with and without carcinoma (P > . 05). Cytologic atypia was present in 8 of 17 patients with carcinoma and 20 of 58 patients without carcinoma (P > .05). CONCLUSIONS: Clinical factors were not helpful in predicting carcinoma in patients with an indeterminate FNAB finding and thus cannot be used to reliably select patients for more extensive thyroidectomy.

Supraclavicular lymphadenopathy: the spectrum of pathology and evaluation by fine-needle aspiration biopsy.

Fine-needle aspiration biopsy (FNAB) has emerged as an important modality for the evaluation of supraclavicular lymphadenopathy. To determine the spectrum of pathology and the efficacy of FNAB, all patients with supraclavicular lymphadenopathy evaluated from 1990 to 1997 were analyzed for: 1) a prior history of malignancy; and 2) the side of the abnormal lymph node, FNAB result, and final pathologic diagnosis. FNAB was used to evaluate left- and right-sided supraclavicular lymphadenopathy in 33 and 19 patients, respectively. FNAB was malignant in 37 patients (71%), benign in 4 patients (8%), nondiagnostic in 6 patients (11%), and suspicious in 5 patients (10%). A prior history of malignancy was present in 30 patients and, of these, 23 (77%) had a malignant FNAB compared with 14 of 22 patients (64%) with no previous history of cancer (P > 0.05). Of the 37 patients with a malignant FNAB, 22 (59%) were from a left supraclavicular node. Abdominal and pelvic tumors uniformly metastasized to a left supraclavicular lymph node, whereas malignancies of the head and neck, thorax, breast, and skin and lymphoma showed no significant difference in laterality. There were no false positive or false negative FNAB results. In conclusion, the yield of FNAB is similar in patients with or without a history of malignancy, justifying the routine use of FNAB as the initial diagnostic test for evaluation of patients with supraclavicular lymphadenopathy. However, FNAB is not definitive in 21 per cent of patients with supraclavicular lymphadenopathy, emphasizing the importance of selective excisional biopsy.

Follow-up evaluation and clinical course of patients with benign nodular thyroid disease.

Reliance on fine-needle aspiration biopsy (FNAB) in determining which patients with a thyroid nodule can be observed depends on a low false-negative rate. The purpose of this study was to determine the false-negative rate of FNAB, the utility of routine repeat FNAB, and the clinical course of patients with benign nodular thyroid disease. The records of all patients with nodular thyroid disease evaluated between June 1990 and May 1998 were reviewed. Patients with a benign FNAB were identified, and nodule size, substernal extension, the results of repeat FNAB, clinical course, histologic diagnosis, and length of follow-up were determined. Of the 341 patients referred with nodular thyroid disease, 121 had a benign FNAB. In 80 patients with a mean nodule size of 3.5 +/- 1.6 cm, clinical follow-up was recommended. The mean duration of follow-up was 20.5 months for 74 patients, and 6 patients were lost to follow-up. Nodule resolution was observed in 7 patients. Repeat FNAB was performed in 45 patients and was benign in 39 (87%), nondiagnostic in 2 (4%), cellular in 3 (7%), and malignant in 1 (2%). Thyroidectomy was performed in the patients with the cellular and malignant aspirates, and the pathology was adenomatous hyperplasia (2), follicular adenoma (1), and papillary carcinoma (1). Thyroidectomy was performed for increasing nodule size and/or compressive symptoms in 41 patients with a mean nodule size of 5.7 +/- 1.9 cm, 19 of whom had substernal extension (P < 0.05). Pathology included benign disease in 39, papillary cancer in 1, and lymphoma arising in Hashimoto's thyroiditis in 1 patient. Given that repeat FNAB was of value in only 1 patient and the false-negative rate for FNAB was only 2.5 per cent, the routine use of repeat FNAB in patients with benign nodular thyroid disease may not be justified. Development of compressive symptoms and diagnosis of unsuspected malignancy in patients with nodule enlargement, including lymphoma in patients with Hashimoto's thyroiditis, underscores the importance of long-term follow-up.

Refined use of scintigraphy in the evaluation of nodular thyroid disease.

BACKGROUND: Scintigraphy has been advocated in patients with a thyroid nodule when fine needle aspiration biopsy (FNAB) is not definitive. The purpose of this study was to determine the incidence of hyperfunctioning nodules in patients without a definitive FNAB, the correlation of serum thyrotropin (TSH) levels with the functional status of a nodule, and whether a sensitive TSH assay can be used in lieu of scintigraphy. METHODS: From 1990 to 1996, patients with a thyroid nodule were evaluated with FNAB and serum TSH measurement. Iodine-123 scintigraphy was reserved for patients without a definitive FNAB and was correlated with TSH levels. RESULTS: Of 356 patients with a thyroid nodule, 102 did not have a definitive FNAB. A hyperfunctioning nodule was diagnosed in 14 of the 102 patients. A low TSH level was detected in 12 (86%) of 14 patients with a hyperfunctioning nodule (mean = 0.04 +/- 0.38 microIU/mL) and only 20 (23%) of 88 patients with a hypofunctioning nodule (mean = 0.87 +/- 4.11 microIU/mL) (P < .05). Only 2 of 70 (2.8%) patients with a normal or increased TSH level had a hyperfunctioning nodule. CONCLUSIONS: A 14% incidence of hyperfunctioning nodules in patients without a definitive FNAB warrants the use of scintigraphy but only when serum TSH levels are low, thus avoiding unnecessary scans in 91% of patients with a thyroid nodule.

Management of follicular and Hürthle cell neoplasms of the thyroid gland.

Management of follicular and Hürthle cell neoplasms of the thyroid gland is a common clinical problem. A diagnosis of follicular or Hürthle cell carcinoma cannot be made from a fine-needle aspiration biopsy alone because it requires histologic demonstration of capsular or vascular invasion. Thyroid lobectomy and isthmusectomy is adequate treatment of benign follicular or Hürthle cell adenoma and minimally invasive follicular carcinoma. Total thyroidectomy, radioiodine ablation, and thyrotropin-suppressive doses of thyroid hormone is advocated for the invasive subtype of follicular carcinoma and all Hürthle cell carcinomas. Monitoring of serum thyroglobulin levels postoperatively is important for detection of recurrent disease.

The adrenal incidentaloma: guidelines for evaluation and recommendations for management.

Adrenal masses are identified incidentally on up to 1.5% of all abdominal CT scans. The appropriate evaluation and management of these "incidentalomas" remains controversial and centers on questions of function and potential for malignancy. Functional evaluation includes consideration of the diagnoses of aldosteronoma, pheochromocytoma, and corticosteroid-producing adenoma. Potential for malignancy can be evaluated using a number of imaging modalities, although none is diagnostic. Size remains one of the best criteria for assessing potential for malignancy.

Inwardly rectifying K+ channels in dispersed bovine parathyroid cells.

Excitation-secretion coupling in various endocrine cells is dependent on membrane voltage which is controlled by ion channels. In order to characterize and determine the functional significance of voltage-gated ion channels in the parathyroid cell, the patch clamp technique was used in cell-attached and whole cell configurations to study single channel and whole cell currents in dispersed bovine parathyroid cells. Whole cell voltage clamp recordings from dissociated bovine parathyroid cells were obtained in a physiologic solution containing (in mM): 140 NaCl, 5.4 KCI, 2 CaCl2, and 2 MgCl2. The pipette (intracellular) solution contained (in mM) 145 KAsp, 10(-5) CaCl2, and 2 MgCl2. Currents were recorded in response to 20-mV incremental changes in voltage of 300-ms duration every 3 s from -80 to +40 mV and from -40 to -140 mV. There was a small outward current recorded in response to 300-ms pulses of 20-mV increments from -80 to +40 mV. A large inward current was recorded following hyperpolarization of the parathyroid cell from -40 to -140 mV. The reversal potential for the current was -60 to -65 mV, suggesting that the majority of the current is carried by a channel that is K+ selective. Our results suggest that the whole cell currents of dispersed bovine parathyroid cells in physiologic extracellular solution include an in inwardly rectifying K+ current which is open at low intracellular calcium concentration. This inwardly rectifying K+ channel is likely to play a major role in maintaining negative membrane potential by opposing calcium-induced depolarization of the parathyroid cell and, as a result, may have an important role in regulation of PTH secretion.

The association of intra-abdominal infection and abdominal wound dehiscence.

Concurrent infection is a risk factor for abdominal wound dehiscence. We reviewed our experience with fascial dehiscence to determine the incidence and to identify prognostic factors for associated intra-abdominal infection. Over a 7-year period, 107 patients with abdominal wound dehiscence were identified. Seventeen were managed nonoperatively, and 90 underwent exploratory laparotomy, 43 of whom had no intra-abdominal pathology and 47 of whom had intra-abdominal infections. Demographic factors, comorbid diseases, and potential indicators of systemic infection did not distinguish patients with intra-abdominal infection from those without. Patients with an intra-abdominal infection were more likely to have undergone an emergency operation (74% vs 48%; P < 0.02), an operation on the colon (55% vs 25%; P < 0.005), or an operation with a higher wound classification (P < 0.02). Mortality was higher in patients with intra-abdominal infection than in those without (44% vs 20%; P < 0.02). Wound dehiscence after emergent operations, and operations with a higher wound classification, especially those involving the colon, should raise concern for intra-abdominal infection. Thorough abdominal exploration should be performed at the time of dehiscence repair. Before nonoperative management is chosen, intra-abdominal infection should be excluded.