A non-antibacterial chemically-modified tetracycline inhibits mammalian collagenase activity

Tetracyclines (including the semi-synthetic analogues, minocycline and doxycycline) are considered useful adjuncts in periodontal therapy because they suppress Gram-negative periodontopathogens. Recently, these antibiotics were found to inhibit mammalian collagenase activity, a property which may also be of therapeutic value. It has been suggested that the anti-collagenase properties of the tetracyclines are independent of their antibiotic efficacy. To advance this hypothesis further, we chemically converted tetracycline hydrochloride to its non-antimicrobial analogue, de-dimethylaminotetracycline. This chemically-modified tetracycline (CMT), although no longer an effective antibiotic, was found to inhibit the in vitro activity of collagenase from partially purified extracts of human rheumatoid synovial tissue and rachitic rat epiphysis. In a preliminary in vivo study, pathologically-excessive collagenase in skin and gingiva was induced by rendering adult male rats diabetic, and the oral administration of CMT to these rats significantly reduced the excessive collagenase activity in both tissues. Moreover, CMT administration did not affect the severe hyperglycemia in these rats but did prevent, at least in part, the diabetes-induced loss of body weight, skin weight, and skin collagen mass; these effects suggest a lack of toxicity in this animal model. A proposed clinical advantage of CMT over conventional tetracyclines, in the treatment of diseases characterized by excessive collagenolytic activity, is the lack of development of antibiotic-resistant micro-organisms during prolonged use. However, the consideration of clinical trials to support this hypothesis must await further laboratory and extensive toxicity tests.

Opposing actions of intact and N-terminal fragments of the human prolactin/growth hormone family members on angiogenesis: an efficient mechanism for the regulation of angiogenesis

Angiogenesis, the process of development of a new microvasculature, is regulated by a balance of positive and negative factors. We show both in vivo and in vitro that the members of the human prolactin/growth hormone family, i.e., human prolactin, human growth hormone, human placental lactogen, and human growth hormone variant are angiogenic whereas their respective 16-kDa N-terminal fragments are antiangiogenic. The opposite actions are regulated in part via activation or inhibition of mitogen-activated protein kinase signaling pathway. In addition, the N-terminal fragments stimulate expression of type 1 plasminogen activator inhibitor whereas the intact molecules have no effect, an observation consistent with the fragments acting via separate receptors. The concept that a single molecule encodes both angiogenic and antiangiogenic peptides represents an efficient model for regulating the balance of positive and negative factors controlling angiogenesis. This hypothesis has potential physiological importance for the control of the vascular connection between the fetal and maternal circulations in the placenta, where human prolactin, human placental lactogen, and human growth hormone variant are expressed.

Activation of mitogen-activated protein kinases by vascular endothelial growth factor and basic fibroblast growth factor in capillary endothelial cells is inhibited by the antiangiogenic factor 16-kDa N-terminal fragment of prolactin

A number of factors both stimulating and inhibiting angiogenesis have been described. In the current work, we demonstrate that the angiogenic factor vascular endothelial growth factor (VEGF) activates mitogen-activated protein kinase (MAPK) as has been previously shown for basic fibroblast growth factor. The antiagiogenic factor 16-kDa N-terminal fragment of human prolactin inhibits activation of MAPK distal to autophosphorylation of the putative VEGF receptor, Flk-1, and phospholipase C-gamma. These data show that activation and inhibition of MAPK may play a central role in the control of angiogenesis.

Microplastics occurrence in the Tyrrhenian waters and in the gastrointestinal tract of two congener species of seabreams

In this work it is reported for the first time the characterization of microplastics from sea water samples and in two congener species of seabreams: Pagellus erythrinus and P. bogaraveo, Mediterranean fish species of great commercial importance. An experimental survey was conducted on May-June 2017 in the southernmost part of the Tyrrhenian Sea. Microplastics found in the sea water and in the grastrointestinal tract of two teleosts were characterized by Raman and IR spectroscopies. Microplastics found in sea water samples appeared in the form of fragments made of plastics of low and high density (PVC and LPDE). All the microplastics found in fish belonged to Nylon 66, typical fibers used in industry and in fisheries. Our findings highlighted the importance of further studies along the food web chain for a better understanding of the diffusion and possible consequences of this terrible threat.

An anatomical comparison of the human and bovine thoracolumbar spine

The bovine spine has been frequently selected as the model for in vitro mechanical studies. A comparative anatomical study has been presented describing important differences and similarities between selected areas in the adult human and calf thoracolumbar spinal segment. Differences in column length and curvature were observed. The total length of the adult bovine vertebral column was found to be on average 209 cm longer than the adult human spine. Equivalent thoracolumbar lengths were obtained by selecting 6-8 week-old dairy calves, which because of their young age had the benefit of consistent bone density. The bovine spine was found to have only a single cervical lordotic curve and a single thoracolumbar kyphotic curve (2). A quantitative comparison of selected dimensions of vertebrae T6, T12, and L3 was performed, and significant findings are discussed. The bovine spinous processes were found to be on average 111% greater in length at level T6, which contributed to a 56% greater total anterior/posterior length at this level in comparison to the vertebrae of an adult male. A 23% greater bovine intertransverse length at level L3 was also shown. The orientation of the human and bovine superior facets, while being in the same general plane and direction, varied as much as 10.5 and 107% at vertebral level L3 on the two axes measured. These significantly different measurements were considered important factors that can influence experimental results when using the bovine spine as a model.

Transduction mechanisms involved in the regulation of myogenic activity

Vascular smooth muscle has the ability to exist in a state of maintained partial constriction. This state of partial activation is initiated and/or maintained by the mechanical effects of distending pressure acting on the vascular wall. The intrinsic ability of vascular smooth muscle to respond to these mechanical forces is referred to as the myogenic mechanism. Within the past decade the signaling mechanisms responsible for mechanotransduction of myogenic phenomena have been the focus of extensive research. Two areas of active investigation include (1) the modulation of membrane ionic conductances by pressure/stretch and (2) the pressure/stretch-induced generation of second messengers known to be involved in vascular smooth muscle contraction. This review summarizes recent work aimed at understanding the mechanotransduction process in vascular smooth muscle.

Inhibition of gonadotropin hormone-releasing hormone release by prolactin from GT1 neuronal cell lines through prolactin receptors

High levels of prolactin (PRL) are associated with inhibition of luteinizing hormone secretion in several mammalian species. We asked whether this phenomenon could be explained by a direct inhibitory action of PRL on hypothalamic gonadotropin hormone-releasing hormone (GnRH) neurons. The ability of PRL to suppress GnRH release and expression was tested in the highly differentiated GT1 GnRH cell lines. In static culture, nanomolar concentrations of either rat or mouse PRL inhibited the release of GnRH in a dose-dependent fashion. PRL treatment for 24 hr also decreased GnRH mRNA levels determined by Northern analysis. The cells were shown to express the PRL receptor gene, and the mRNAs for both the short and long forms were present by Northern and PCR analysis, although the short form was more abundant. In Western blots with monoclonal antibody against the rat liver PRL receptor, the short 42-kDa form of the receptor was observed. These results demonstrate that PRL inhibits GnRH release and possibly gene expression in GnRH neurons. This action appears to be mediated through prolactin receptors expressed by the cells.

Mammal-specific, ERK-dependent, caldesmon phosphorylation in smooth muscle. Quantitation using novel anti-phosphopeptide antibodies

Extracellular signal-regulated kinases (ERKs) phosphorylate the high molecular mass isoform of the actin-binding protein caldesmon (h-CaD) at two sites (Ser(759) and Ser(789)) during smooth muscle stimulation. To investigate the role of phosphorylation at these sites, antibodies were generated against phosphopeptides analogous to the sequences around Ser(759) and Ser(789). Affinity-purified antibodies were phosho- and sequence-specific. The major site of phosphorylation in h-CaD in porcine carotid arterial muscle strips was at Ser(789); however, the amount of phosphate did not vary appreciably with either KCl or phorbol ester stimulation. Phosphorylation at Ser(759) of h-CaD was almost undetectable (<0.005 mol of phosphate/mol of protein). Moreover, phosphorylation of the low molecular mass isoform of the protein (l-CaD) at the site analogous to Ser(789) was greater in serum-stimulated cultured smooth muscle cells than in serum-starved cells. Serum-stimulated l-CaD phosphorylation was attenuated by the protein kinase inhibitor PD98059. These data 1) identify Ser(789) of h-CaD as the major site of ERK-dependent phosphorylation in carotid arteries; 2) show that the level of phosphorylation at Ser(789) is relatively constant following carotid arterial muscle stimulation, despite an increase in total protein phosphate content; and 3) suggest a functional role for ERK-dependent l-CaD phosphorylation in cell division.

Sequence of sites on ATP-citrate lyase and phosphatase inhibitor 2 phosphorylated by multifunctional protein kinase (a glycogen synthase kinase 3 like kinase)

Multifunctional protein kinase (MFPK) phosphorylates ATP-citrate lyase on peptide B on two sites, BT and BS, on threonine and serine, respectively, inhibitor 2 on a threonyl residue, and glycogen synthase at sites 2 and 3. The phosphorylation sites BT and BS of ATP-citrate lyase are dependent on prior phosphorylation at site A whereas site A phosphorylation is decreased by prior phosphorylation at sites BT and BS. To study the MFPK recognition sites and the site-site interactions, the amino acid sequences of ATP-citrate lyase peptide B and inhibitor 2 were determined and compared to each other and to glycogen synthase sites 3-5. The sequence of the tryptic peptide containing the two phosphorylation sites of peptide B is -Phe-Leu-Leu-Asn-Ala-Ser-Gly-Ser-Thr-Ser-Thr(P)-Pro-Ala-Pro-Ser(P)-Arg-, and the sequence of the MFPK phosphorylation site of inhibitor 2 is -Ile-Asp-Glu-Pro-Ser-Thr(P)-Pro-Tyr-. This inhibitor 2 site is identical with the site phosphorylated by glycogen synthase kinase 3/FA. These results suggest that at least some of the sites phosphorylated by MFPK (BT of ATP-citrate lyase, Thr 72 of inhibitor 2, and sites 3b and 4 of glycogen synthase) contain a Ser/Thr flanked by a carboxyl-terminal proline. However, as MFPK did not phosphorylate a series of peptides containing the -X-Thr/Ser-Pro-X- sequence, this minimum consensus sequence is not sufficient for phosphorylation by MFPK.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphoid interstitial pneumonia after allogeneic bone marrow transplantation. A possible manifestation of chronic graft-versus-host disease

Interstitial pneumonia (IP) is a frequent and serious complication of bone marrow transplantation with a median time of onset about 2 months posttransplant. Most cases result either from toxicity of radiation and chemotherapy or from infection with pathogens such as cytomegalovirus. Described are two patients with chronic graft-versus-host disease (GVHD) who presented with late-onset IP 242 and 632 days posttransplant. Histologic examination of lung biopsy specimens disclosed a lymphoid interstitial pneumonia (LIP) in both cases. The major lymphocyte subset found in bronchoalveolar lavages and lung tissue was OKT8(+) and showed a positive dot staining for acid phosphatase. Contrary to peripheral blood mononuclear cells, most OKT8(+) lymphocytes in the lungs were OKT3(-). Since acute GVHD lesions are mediated mainly by cytotoxic T-lymphocytes, our data suggest that LIP in marrow-grafted patients may be a manifestation of chronic GVHD. It should be distinguished from the more common types of IP encountered following bone marrow transplantation.

Regulation of vascular endothelial growth factor expression by cAMP in rat aortic smooth muscle cells

Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen which stimulates angiogenesis. VEGF is regulated by multiple factors such as hypoxia, phorbol esters, and growth factors. However, data concerning the expression of VEGF in the different vascular cell types and its regulation by cAMP are not available. In the present study, we have investigated the effect of adenylate cyclase activation on VEGF mRNA expression in rat vascular cells in primary culture. Basal VEGF expression is greater in smooth muscle cells than in endothelial cells and fibroblasts. A 4-h treatment with forskolin (10(-5) M) induced a 2-fold stimulation of VEGF mRNA expression in smooth muscle cells and fibroblasts, but, in contrast, did not affect VEGF expression in endothelial cells. In smooth muscle cells, a pharmacologically induced increase in intracellular cAMP levels using iloprost or isoprenaline led to a rise in VEGF mRNA expression comparable to that induced by forskolin. Adenosine, which increases cAMP levels in smooth muscle cells, also increases VEGF expression. Moreover, the 2.2-fold stimulation of VEGF expression by adenosine was enhanced following a cotreatment with cobalt chloride (a hypoxia miming agent). The observed additive effect (4.3-fold increase) suggests that these two factors, hypoxia and adenosine, regulate VEGF mRNA expression in smooth muscle cells by independent mechanisms.

cDNA sequence of rat liver fructose-1,6-bisphosphatase and evidence for down-regulation of its mRNA by insulin

A coding-length clone of rat liver fructose-1,6-bisphosphatase (EC 3.1.3.11) was isolated by immunological screening of a cDNA library in lambda gt11. Its identity was verified by comparing the deduced amino acid sequence with that obtained by direct sequencing of a complete set of CNBr and proteolytic peptides from the purified protein. The enzyme subunit is composed of 362 amino acids and has N-acetylvaline as the amino-terminal residue. The cDNA, 1255 base pairs (bp) long, consisted of 1086 bp of coding region, 15 bp of 5' untranslated sequence, and 154 bp at the 3' untranslated end. The 3' untranslated sequence contained a polyadenylylation signal (AATAAA) followed after 30 bp by a stretch of 7 adenines at the end of the clone. The deduced amino acid sequence was identical to the primary sequence of the protein and confirmed the alignment of five nonoverlapping peptides. It also confirmed the 27-residue extension, unique to the rat liver subunit, ending with a carboxyl-terminal phenylalanine. RNA blot analyses using the radiolabeled liver cDNA as a probe revealed a single band of fructose-1,6-bisphosphatase mRNA, 1.4 kilobases long, in liver and kidney but not in nongluconeogenic tissues. Fructose-1,6-bisphosphatase mRNA was increased 10-fold in livers from diabetic rats and was reduced to control levels after 24 hr of insulin treatment, suggesting that the changes in enzyme activity observed in diabetes and after insulin treatment are due to alterations in mRNA abundance.

Role of disorder in the thermodynamics and atomic dynamics of glasses

We measured the density of vibrational states (DOS) and the specific heat of various glassy and crystalline polymorphs of SiO2. The typical (ambient) glass shows a well-known excess of specific heat relative to the typical crystal (α-quartz). This, however, holds when comparing a lower-density glass to a higher-density crystal. For glassy and crystalline polymorphs with matched densities, the DOS of the glass appears as the smoothed counterpart of the DOS of the corresponding crystal; it reveals the same number of the excess states relative to the Debye model, the same number of all states in the low-energy region, and it provides the same specific heat. This shows that glasses have higher specific heat than crystals not due to disorder, but because the typical glass has lower density than the typical crystal.

Integrin-mediated reduction in vascular smooth muscle [Ca2+]i induced by RGD-containing peptide

It has previously been shown that synthetic peptides containing the sequence arginine-glycine-aspartic acid (RGD) cause vasodilation by activation of alpha(v)beta3-integrin present on vascular smooth muscle (VSM) cells. The purpose of this study was to determine whether this dilatory effect is mediated by a reduction in VSM cytosolic Ca2+ concentration ([Ca2+]i). First-order arterioles from the rat cremaster were isolated, cannulated, and pressurized. [Ca2+]i was quantitated from the ratio of emitted fluorescence intensity during alternate excitation of fura 2-loaded vessels at 340 and 380 nm. Cyclo(-Arg-Gly-Asp-D-Phe-Val) (cycloRGD; 0.21-210 microM) produced a concentration-dependent dilation of arterioles that had developed basal myogenic tone. Over the entire concentration range tested, [Ca2+]i decreased from 91 +/- 6 to 27 +/- 4 nM (69.7 +/- 5.0% reduction). In association with the decrease in [Ca2+]i, arteriolar lumen diameter increased from 89 +/- 8 to 184 +/- 8 pm (89.8 +/- 1.8% dilation). At intermediate concentrations, cycloRGD induced rhythmic spiking of Ca2+ superimposed on the concentration-dependent lowering of basal [Ca2+]i. These data directly link integrin activation with alterations in Ca2+ regulation, the net effect of which is a reduction in [Ca2+]i. These data further suggest that integrins, through their role in mediating cellular attachment to the extracellular matrix and in cellular signaling involving Ca2+, could provide a logical link to mechanotransduction and myogenic phenomena.

Multi-component modeling of quasielastic neutron scattering from phospholipid membranes

We investigated molecular motions in the 0.3-350 ps time range of D2O-hydrated bilayers of 1-palmitoyl-oleoyl-sn-glycero-phosphocholine and 1,2-dimyristoyl-sn-glycero-phosphocholine in the liquid phase by quasielastic neutron scattering. Model analysis of sets of spectra covering scale lengths from 4.8 to 30 Å revealed the presence of three types of motion taking place on well-separated time scales: (i) slow diffusion of the whole phospholipid molecules in a confined cylindrical region; (ii) conformational motion of the phospholipid chains; and (iii) fast uniaxial rotation of the hydrogen atoms around their carbon atoms. Based on theoretical models for the hydrogen dynamics in phospholipids, the spatial extent of these motions was analysed in detail and the results were compared with existing literature data. The complex dynamics of protons was described in terms of elemental dynamical processes involving different parts of the phospholipid chain on whose motions the hydrogen atoms ride.

Regional variation in resistance artery diameter responses to alpha-adrenergic stimulation during pregnancy

Whole animal pressor responses are blunted during pregnancy; yet, uterine arteries, paradoxically, become significantly more sensitive to the constrictor effects of phenylephrine (PE). The objectives herein were to investigate 1) the regional variation (uterine vs. mesenteric arteries) in dose-lumen diameter relationship to alpha-adrenergic stimulation during pregnancy, and 2) the selectivity of these sensitivity shifts for this pathway (PE vs. KCl). Lumen diameter was measured in isolated, pressurized (50 mmHg) arterial segments from age-matched virgin (nonpregnant; NP) and late pregnant (LP; days 19-20) Sprague-Dawley rats. Uterine arcuate vs. mesenteric arteries from NP rats were equally sensitive to either vasoconstrictor. Arcuate arteries from LP rats, however, were 4.5-fold more sensitive to PE (P < 0.01) compared with those from NP controls. Furthermore, diameter curves became superimposed at [PE] > or = 0.1 microM, even though initial diameter of arcuate arteries from LP rats was significantly larger (P < 0.001). Conversely, mesenteric arteries from LP rats were three-fold less sensitive to PE (P < 0.02), and the diameter curve displayed a corresponding parallel rightward shift. Pregnancy did not affect the sensitivity to KCl depolarization in either arcuate or mesenteric arteries. The percent reduction in lumen diameter to the maximum [KCl] was significantly decreased only in arcuate arteries from LP rats (P < 0.001). Thus, during pregnancy, divergent constrictor responses specific to alpha-adrenergic stimulation occur in resistance arteries from the uterine vs. splanchnic circulations. Consequently, concentrations of PE that are subthreshold in NP uterine arteries can elicit large changes in lumen diameter and thereby have a pronounced effect on uterine vascular resistance in the pregnant state.

Inflammation as a Predictor of Recurrent Ventricular Tachycardia After Ablation in Patients With Myocarditis

BACKGROUND

Little is known about the risk stratification of patients with myocarditis undergoing ventricular tachycardia (VT) ablation.

OBJECTIVES

This study sought to describe VT ablation results and identify factors associated with arrhythmia recurrences in a cohort of patients with myocarditis.

METHODS

The authors enrolled 125 consecutive patients with myocarditis, undergoing VT ablation. Before ablation, disease stage was evaluated, to identify active (AM) versus previous myocarditis (PM). The primary study endpoint was assessment of VT recurrences by 12-month follow-up. Predictors of VT recurrences were retrospectively identified.

RESULTS

All patients (age 51 ± 14 years, 91% men, left ventricular ejection fraction 52% ± 9%) had history of myocarditis diagnosed by endomyocardial biopsy (59%) and/or cardiac magnetic resonance (90%). Furthermore, all had multiple episodes of drug-refractory VTs. Multimodal pre-procedural staging identified 47 patients with AM (38%) and 78 patients with PM (62%). All patients showed low-voltage areas (LVA) at electroanatomical map (97% epicardial or endoepicardial); of them, 25 (20%) had wide borderzone (WBZ, constituting >50% of the whole LVA). VT recurrences were documented in 25 patients (20%) by 12 months, and in 43 (34%) by last follow-up (median 63 months; interquartile range: 39 to 87). At multivariable analysis, AM stage was the only predictor of VT recurrences by 12 months (hazard ratio: 9.5; 95% confidence interval: 2.6 to 35.3; p < 0.001), whereas both AM stage and WBZ were associated with arrhythmia recurrences anytime during follow-up. No VT episodes were found after redo ablation was performed in 23 patients during PM stage.

CONCLUSION

Our findings suggest that VT ablation should be avoided during AM, but is often of benefit for recurrent VT after the acute phase of myocarditis.

Speed-dependent modulation of phase variations on a step-by-step basis and its impact on the consistency of interlimb coordination during quadrupedal locomotion in intact adult cats

It is well established that stance duration changes more than swing duration for a given change in cycle duration. Small variations in cycle duration are also observed at any given speed on a step-by-step basis. To evaluate the step-by-step effect of speed on phase variations, we measured the slopes of the linear regressions between the phases (i.e., stance, swing) and cycle duration during individual episodes at different treadmill speeds in five adult cats. We also determined the pattern of dominance, defined as the phase that varies most with cycle duration. We found a significant effect of speed on hindlimb phase variations, with significant differences observed between the slowest speed of 0.3 m/s compared with faster speeds. Moreover, although patterns of phase dominance were primarily stance/extensor dominated at the slowest speeds, as speed increased the patterns were increasingly categorized as covarying, whereby both stance/extensor and swing/flexor phases changed in approximately equal proportion with cycle duration. Speed significantly affected the relative duration of support periods as well as interlimb phasing between homolateral and diagonal pairs of limbs but not between homologous pairs of limbs. Speed also significantly affected the consistency of interlimb coordination on a step-by-step basis, being less consistent at the slowest speed of 0.3 m/s compared with faster speeds. We found a strong linear relationship between hindlimb phase variations and the consistency of interlimb coordination. Therefore, results show that phase variations on a step-by-step basis are modulated by speed, which appears to influence the consistency of interlimb coordination.

Long-term evaluation of patients with apical hypertrophic cardiomyopathy. Correlation between quantitative echocardiographic assessment of apical hypertrophy and clinical-electrocardiographic findings

Apical hypertrophic cardiomyopathy (AHCM) is characterized by primary hypertrophy localized exclusively in the apex of the left ventricle. Previous studies have indicated that AHCM results in a unique combination of cross-sectional echocardiographic (CSE) and ECG findings ('giant' T wave inversion and high R wave voltage in the precordial leads). The aims of this study were: (1) to assess the degree of AHCM in a quantitative fashion (2) to evaluate the possible relationship between apical hypertrophy, quantitatively determined, and ECG findings in patients with AHCM (3) to verify the changes in echocardiographic and ECG parameters over time (4) to define the relationship between the severity of AHCM and the clinical course of such patients. Eleven selected patients with AHCM were studied for an average 6 year follow-up period; there were seven men and four women (age from 18 to 62 years, mean 49). Apical hypertrophy was assessed quantitatively by determining the muscle cross-sectional area in the apical region, which was considered an index of myocardial mass. From the end-diastolic apical four chamber view, endocardial and epicardial contours were digitized in order to obtain the total muscle cross-sectional area of the left ventricle. The walls of the left ventricle were then divided into three regions (basal, intermediate, apical). The final value of each cross-sectional muscle area was obtained from the mean measurements of four independent and blinded observers. In AHCM the apical muscle cross-sectional area (AMA) ranged from 10.3 to 17.9 cm2, mean 13.2 +/- 2.6 cm2.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium and mechanotransduction of the myogenic response

The purpose of this study was to measure vascular smooth muscle (VSM) cytosolic calcium ([Ca2+]i) during the myogenic response. We examined the temporal and steady-state relationships between lumen diameter and VSM [Ca2+]i in isolated arterioles exposed to step changes in intravascular pressure. We also studied the relationship between step sizes in intravascular pressure and changes in [Ca2+]i. First-order arterioles from the hamster cheek pouch were isolated, cannulated, and pressurized. [Ca2+]i was quantified using the ratio of emitted fluorescence intensity (R340/380) during alternate excitation of fura 2-loaded vessels at 340 and 380 nm. Stepwise increases in transmural pressure elicited corresponding increases in steady-state [Ca2+]i and myogenic constriction. From a common baseline pressure, the initial rise in [Ca2+]i after a step change in pressure was directly related to the magnitude of the step size and of the distension caused by that pressure step. This supports the theory that there is a relationship between the initial distension of the vessel and the initial [Ca2+]i change. Also, increasing the size of the step change in pressure resulted in a greater myogenic response, yet no difference in the steady-state [Ca2+]i was detected, which suggests that Ca2+ is not the principal or only determinant of steady-state constriction. Finally, larger increases in [Ca2+]i do not necessarily augment the myogenic response, which suggests that some minimal rise in [Ca2+]i is required to elicit myogenic vasoconstriction. Collectively, these data suggest the presence of a separate, Ca(2+)-independent regulatory system.

Arthroscopic surgery of the shoulder

Arthroscopy of the shoulder is well established as a diagnostic procedure. It carries a greater degree of accuracy than conventional imaging techniques and in addition allows the assessment of instability and the degree of mechanical derangement inside the joint. Arthroscopic surgical procedures in the shoulder are in the developing stage. Arthroscopic acromioplasty for impingement syndrome has been shown to be a safe, effective procedure and probably better than conventional surgery. In the older patient, arthroscopic debridement of the rotator cuff is very effective at relieving pain. Arthroscopic surgery for removal of loose bodies and of a torn glenoid labrum would be the current recommended procedure rather than open surgery. Other rapidly developing areas of potential benefit are in the arthroscopic stabilisation of the dislocating shoulder and synovectomy of the shoulder in rheumatoid arthritis and other synovial conditions. The role of arthroscopy in the frozen shoulder is not clearly established although certainly it is the diagnostic tool of first choice in this condition.

16K human prolactin inhibits vascular endothelial growth factor-induced activation of Ras in capillary endothelial cells

Signaling pathways mediating the antiangiogenic action of 16K human (h)PRL include inhibition of vascular endothelial growth factor (VEGF)-induced activation of the mitogen-activated protein kinases (MAPK). To determine at which step 16K hPRL acts to inhibit VEGF-induced MAPK activation, we assessed more proximal events in the signaling cascade. 16K hPRL treatment blocked VEGF-induced Raf-1 activation as well as its translocation to the plasma membrane. 16K hPRL indirectly increased cAMP levels; however, the blockade of Raf-1 activation was not dependent on the stimulation of cAMP-dependent protein kinase (PKA), but rather on the inhibition of the GTP-bound Ras. The VEGF-induced tyrosine phosphorylation of the VEGF receptor, Flk-1, and its association with the Shc/Grb2/Ras-GAP (guanosine triphosphatase-activating protein) complex were unaffected by 16K hPRL treatment. In contrast, 16K hPRL prevented the VEGF-induced phosphorylation and dissociation of Sos from Grb2 at 5 min, consistent with inhibition by 16K hPRL of the MEK/MAPK feedback on Sos. The inhibition of Ras activation was paralleled by the increased phosphorylation of 120 kDa proteins comigrating with Ras-GAP. Taken together, these findings show that 16K hPRL inhibits the VEGF-induced Ras activation; this antagonism represents a novel and potentially important mechanism for the control of angiogenesis.