Spinal cord monoaminergic system response to age and cold-acclimatization in muscovy duckling

The effect of age and cold acclimatization on the regional distribution of monoamines in duckling spinal cord was studied. In thermoneutral controls (TN), the high dopamine (DA) to norepinephrine (NE) ratios (0.25 at 4 weeks of age and 0.15 at 6 weeks of age) suggest the presence of specific (non precursor) dopaminergic pools in cervical spinal cord. DA levels and the ratio of DA to NE were lowered by age and cold exposure in the cervical cord. In TN ducklings, serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) showed a decline with age in the spinal cord, indicating that this system is affected with development, whereas cold exposure prevents this decrease. The contents of 5-HT (+58%), 5-HIAA (+93%) and the ratio of 5-HIAA to 5-HT (+50%) are higher in the cervical spinal cord of cold acclimated than in TN ducklings. These results indicate that central monoaminergic systems are markedly affected by age and cold exposure.

Osteological investigations of the incidence of cranial alterations in domestic ducks (Anas platyrhynchos f. dom.) with feather crests

The feather crest of the domestic duck (Anas platyrhynchos f. dom.) represents a peculiar mutation of the integument of the head, which has been known since the 17th century. In literature this is described as a variety with malformations in skull and brain anatomy in which various central nervous deficiencies in affected birds are possible. Our examinations demonstrated several conspicuous anatomical alterations in the skulls of domestic ducks with feather crests. Osteophytes of different size in the hypodermis of the crest integument were found as well as cranial perforations located in the parieto-occipital region. In morphometric studies, a significant increase in the capacity of the cranium was found in Crested ducks compared to other examined breeds (Abacot Ranger, German Pekin ducks). This increase in cranial capacity in Crested ducks results from the occurrence and enlargement of a tentorial fatty depot during craniogenesis. The formation and enlargement of the fat body can influence cranium growth as long as the cranial bones are not entirely fused. Thus, in comparison to other phenotypically similar domesticated birds like the crested chicken, the expression of feather crests in domestic ducks demonstrates symptomatologic differences. In conclusion, our examinations demonstrate that the skulls of Crested ducks show various peculiar morphological alterations whose genesis is up to now not known with satisfactory accuracy. Further investigations are continuing to assertain whether there are linkages between cranial alterations (malformations of the calvaria, osteophytes, increased capacity of the cranium) and the extremely high prenatal and postnatal mortalities and numerous abnormalities described in crested breeds of the domestic duck.

Arterial vascularization of the uropygial glands (Gl. uropygialis) in geese (Anser anser) and ducks (Anas platyrhynches)

In the present study, arterial vascularization of the uropygial glands (Gl. uropygialis) of 10 adult geese (Anser anser) and 10 adult ducks (Anas platyrhynches) were studied. Takilon was injected into the median coccygeal arteries of six specimens from each species, and Latex (a natural rubber with ammonia) into those of four specimens. Takilon-injected specimens were corrosion casted, and arteries nourishing the gland were revealed via dissection. Vascularization of the uropygial glands of both the goose and the duck was observed to be the right (a. gl. uropygii dextra), left (a. gl. uropygi sinistra) and ventral (a. gl. uropygi ventralis) glandular uropygial arteries, arising from the median coccygeal (a. coccygea media) artery. Both the right and left glandular uropygial arteries were observed, divided into four branches as follows; muscular ramus (ramus muscularis), medial ramus (ramus medialis), ventral ramus (ramus ventralis) and lateral ramus (ramus lateralis). Of these, as the lateral, medial and ventral branches feed the gland, the muscular branch provides blood for the lateral coccygeal (m. coccygealis lateralis) and levator coccygeal (m. levator coccygealis) muscles, and the skin. Among the arteries mentioned above, anastomosis between the first and the second branches of the right ventral uropygial arteries in the five geese and five ducks was found.

The distribution and colocalisation of nicotinamide adenine dinucleotide phosphate reduced-diaphorase (NADPH-d)-/nitric oxide synthase (NOS)-containing neurons in the innervation of the duck ureter

ensp;The distribution and colocalisation of nicotinamide adenine dinucleotide phosphate reduced-diaphorase (NADPH-d)-/nitric oxide synthase (NOS)-containing (nitrergic) neurons in the innervation of the duck ureter have been studied using histochemistry and immunohistochemistry. Quantitative analysis showed that nitrergic neurons made up 60% and 70% of the total intramural and adventitial neuronal populations, respectively. About 40% of intramural nitrergic neurons expressed VIP-immunoreactivity, and about 75% of nitrergic adventitial neurons expressed TH-immunoreactivity. The density of nitrergic adventitial neurons was significantly greater in the lower tract than in the upper and intermediate tracts. Nerve lesioning experiments showed that the majority of ureteral nitrergic innervation was extrinsic in origin; nitrergic adventitial neurons primarily projected caudocranially, whereas NOS-immunoreactive and NOS-/VIP-immunoreactive intramural neurons primarily projected craniocaudally. These findings suggest that, in birds, the nitrergic innervation plays a role in ureteral functions such as epithelial mucosecretion, muscular motility, and the closing and/or opening of the ureteral papilla.

Photostimulation affects gonadotropin-releasing hormone immunoreactivity and activates a distinct neuron population in the hypothalamus of the mallard

To reveal central mechanisms that transduce photic stimuli to sexually related neuroendocrine changes, Fra-2-ir, an inducible immediate-early gene marker of neuronal activation has been consecutively localized with that of GnRH-I in the brain of mallards that were triggered by artificial light at the photosensitive phase of the reproductive cycle. Strong neuronal activation was found in the POM and PVN in response to 1x or 4x 20 h light exposure that was accompanied with an increase of GnRH-ir in the hypothalamus and a dramatic depletion of GnRH-ir from terminals in the median eminence. The Fra-2 and GnRH-ir profiles, however, were not co-localized in any region at any phase of photostimulation. These results demonstrate profound changes of GnRH-ir in the hypothalamus and reveal a distinct, photoresponsive cell population in the anterior hypothalamic area of the mallard.

Regression equations for in vivo estimation of the meat content of Pekin duck carcases

1. Pekin ducks (strain A-44; 108 males and 108 females) were reared on standard diets for 7 weeks, after which the following measurements were taken: body weight (X1), thickness of breast muscles (measured by means of an ultrasonic apparatus; (X2) and length of breast-bone crest (X3). The birds were slaughtered and chilled carcases were dissected, separating meat, skin with subcutaneous and intermuscular fat, and bones. 2. The data were used to derive multiple regression equations for in vivo estimation of the meat content of whole carcases (Y; g). Separate calculations were made on males and females. The above-mentioned traits--X1, X2 and X3 constitute independent variables of those equations. The following equation (calculated on the basis of the data on both sexes) may be recommended for use in breeding work: Y = 0.184X1 + 125.4X2 + 25.12X3 - 255.8 (S(Y) = 39 g).

Localization, morphology and ultrastructure of taste buds in the domestic duck (Cairina moschata domestica L.) oral cavity

The Authors report on localization of the taste buds in epithelium of the palate (70%), the floor of the oral cavity (28%) and the tongue (2%) in Domestic Duck. Each taste bud is oval-shaped, measuring roughly 130 x 60 microm, and communicates with the oral cavity by a short duct. There is topographical correspondence between the buds and the parietal salivary glands. Ultrastructural examination showed the following 4 cell types: 1) light cells--characterized by cytoplasm containing sparse perinuclear filaments, numerous light vesicles, a uniformly granular nucleus. 2) dark cells--with electron-dense cytoplasm, numerous perinuclear filaments, occasional light vesicles, an irregular and densely granular nucleus. 3) intermediate cells--with characteristics common to the two previous cell types. 4) basal cells--located at the ventral part of the button.

Aspects of the functional morphology of the ductus epididymidis in domestic anseriform and galliform birds

The structure of the ductus epididymidis, and its capacity to take up luminal particulate material (India ink) were studied, using scanning and transmission electron microscopy, in the domestic fowl, turkey and Japanese quail (Order Galliformes) and drake (Order Anseriformes). The epithelium appeared contractile and stable structurally, especially in the drake in which, among other cytoskeletal features, abundant perinuclear intermediate filaments radiated peripherally in the principal, nonciliated (Type III) cell. The Golgi complex was well developed, except in the turkey in which it was extremely inconspicuous. Sparsely granulated profiles were the main component of the elaborate endoplasmic reticulum, which was best developed in the drake and least in the turkey. The cell in the turkey was uniquely laden with large aggregates of lipid droplets. Generally, characteristics of a cell active in the synthesis and merocrine secretion of proteinaceous material were evident. There was no evidence of apocrine-like secretion in well-fixed tissues. The cell lacked the capacity to take up luminal India ink particles, and displayed very poorly developed endocytic structural features, which are also probably only selectively and minimally absorptive. Ultrastructural features varied between and within the orders studied, necessitating further studies.

NPY immunoreactivity in endocrine cells of duck pancreas: an ontogenetic study

In the literature, neuropeptide Y (NPY) has been described in the brain and peripheral nerves. More recently, it has also been detected in endocrine cells of hamster, embryonic mouse, and rat pancreas. However, the presence of NPY in avian embryos and the possible colocalization of this peptide with the other pancreatic hormones have not been reported previously. In this study, NPY presence was studied by immunocytochemical methods in the endocrine pancreas of domestic duck during pre- and postnatal development. NPY immunoreactivity (IR) was detected in embryos and adult animals. Around hatching the intensity of IR in endocrine cells decreased. Double immunohistochemical staining revealed that: 1) NPY-IR is extensively colocalized in small and mixed islets with insulin-IR both in embryos and in adults; and 2) in early embryos NPY-IR occasionally colocalized with glucagon and somatostatin. In early embryos, the colocalization of NPY-IR with several pancreatic hormones could be related to the presence of multi-hormonal progenitor cells. The close relation between insulin and NPY, both in embryos and adults, led us to hypothesize a key role for NPY on insulin cells of duck pancreas.

The innervation of the ureter in the duck (Anas platyrhynchos). A morphological and quantitative study

The morphology and distribution of the innervation in the duck ureter were studied using AChE histochemistry and PGP 9.5 immunohistochemistry. The density of AChE positive ganglia and neurons was calculated in the adventitial and muscular layers both in young and adult birds. Moreover, in order to investigate regional differences in neuronal density, separate neuron counts and neuron density calculations were performed for the upper, intermediate and lower parts of the ureter, and the data were statistically evaluated. Three nerve plexuses located in the tunica adventitia, in the tunica muscularis and in the lamina propria respectively, were observed. Both in young and adult ducks, the density of adventitial neurons was significantly greater in the lower tract than in the upper and intermediate tracts. The findings of the present study suggest that, in birds, the innervation may play a role in ureteric functions such as epithelial mucosecretion, muscular motility, and closure and/or opening of the ureteric papilla.

Melanin-concentrating hormone-producing neurons in birds

The peptidergic melanin-concentrating hormone (MCH) system was investigated by immunocytochemistry in several birds. MCH perikarya were found in the periventricular hypothalamic nucleus near the paraventricular organ and in the lateral hypothalamic areas. Immunoreactive fibers were very abundant in the ventral pallidum, in the nucleus of the stria terminalis, and in the septum/diagonal band complex, where immunoreactive pericellular nets were prominent. Many fibers innervated the whole preoptic area, the lateral hypothalamic area, and the infundibular region. Some fibers also reached the dorsal thalamus and the epithalamus. The median eminence contained only sparse projections, and the posterior pituitary was not labeled. Thus, in birds, a neurohormonal role for MCH is not likely. Immunoreactive fibers were observed in other regions, such as the intercollicular nucleus, stratum griseum periventriculare (mesencephalic tectum), central gray, nigral complex (especially the ventral tegmental area), reticular areas, and raphe nuclei. Although no physiological investigation concerning the role of MCH has been performed in birds, the distribution patterns of the immunoreactive perikarya and fibers observed suggest that MCH may be involved in functions similar to those described in rats. In particular, the projections to parts of the limbic system (ventropallidal ganglia, septal complex, hypothalamus, dorsal thalamus, and epithalamus) and to structures concerned with visceral and other sensory information integration suggest that MCH acts as a neuromodulator involved in a wide variety of physiological and behavioral adaptations (arousal) with regard to feeding, drinking, and reproduction.

Factors affecting reproductive performance in captive Mallard ducks

Propagation of wild-strain Mallards (Anas platyrhynchos) in captivity is hindered by low egg fertility. Therefore, we studied the effects of captivity, age, mate choice and isolation on reproductive parameters of Mallards. Captive drakes had smaller immature testes than free-flying Mallard drakes. Captive yearling ducks weighed less than adult ducks at the beginning of the breeding season, but no differences were found between their initial clutch size, egg volume or number of clutches laid. Yearling pairs had lower egg fertility (7%) than adult pairs (80%). Egg fertility was higher (51 vs 21%) in self-chosen pairs than in randomly assigned pairs. Isolation of ducks, however did not influence egg production.

[Growth of the cloacal bursa (bursa of Fabricius) and spleen in ducks]

The growth in weight of both the bursa of Fabricius and the spleen was investigated in different stocks of ducks between hatching and 154 days of age. The data were analysed by fitting the Janoschek growth curve and the allometric formula. Both organs showed rapid growth to their maximum dimensions and early points of inflection. The regression of the cloacal bursa started at about 12 weeks of age in Pekins and Mallards. In the Muscovy, the involution begins beyond the period of investigation. Allometrically, a biphasic relationship was found. Starting with positive allometry, the allometric exponent decreased to negative or isometric (Muscovies) values within the second week of age. If the organ weights are compared on the basis of these allometric relationships, Pekins had bursa weights that were about 30% higher than those in Mallards. For the spleen, there was no difference between wild and domesticated ducks.

Growth of the digestive organs in ducks with considerations on their growth in birds in general

1. Growth of the oesophagus, proventriculus, gizzard, intestine, liver and pancreas weight was investigated in Mallards, White Pekins, Muscovies and a Muscovy x White Pekin cross. The birds varied in age between hatching and 154 d. The data were analysed by fitting both the Janoschek growth curve and the allometric formula. 2. The growth rate of all organs, except the oesophagus, peaked earlier (30 d for Muscovies and 14 d for the other breeds) than body weight and they grew faster to any given percentage of their final weight. In contrast, oesophagus weight showed growth curve characteristics similar to body weight. 3. Oesophagus weight showed simple, slightly negative allometry. The remaining organs followed complex allometry that can approximately be described by 2 allometric stages. The 1st phase was isometric to positive allometric. The 2nd showed marked negative allometry. 4. These growth patterns are assumed to be generally present in birds.

Growth pattern and carcase development in male ducks selected for growth rate

1. Growth patterns of the whole body, eviscerated carcases, breast muscle, leg and thigh muscles and abdominal fat pads were compared in 4 lines (Lines A, B, C, and D) of male ducks selected for market weight (n = 1305) using growth curve analysis, allometric growth analysis and repeated measure analysis. At 49 d of age, Line A was heaviest, followed by Line B, Line C and Line D. 2. Ducks were fed ad libitum under 24-h lighting and 12 or 24 ducks were killed to determine body, carcase, breast-muscle, leg and thigh-muscle, and abdominal fat weights at time points from hatching until 53 d of age. 3. The Weibull function was chosen for growth curve analysis. The asymptote and inflection point from the Weibull growth curves identified 3 lines (Lines B, C, and D) with discrete body and carcase growth patterns but did not distinguish Line A from Line B. In all 4 lines the asymptote ranged from 4437 g to 3008 g for body weight and from 3334 g to 2098 g for carcase weight; the inflection point ranged from 22.5 d to 25.3 d for body weight and from 25.4 d to 29.6 d for carcase weight. 4. The allometric growth coefficient, relative to whole-body growth, was higher than 1.00 for breast muscle and lower than 1.00 for leg and thigh muscles during from 4 d to 53 d of age. 5. Body fat accumulation was estimated by abdominal fat. Line D accumulated more abdominal fat than other lines. The pattern of fat accumulation in Line D was different from Lines A, B and C and there were no differences between Lines A, B and C.

Relationships between kidney mass and body size in some Anseriformes

Relationships between kidney mass (KM) and body mass (BM), body length (BL), and sternum length (SL) were studied in adults of both sexes of 4 Mergini anseriforms: Clangula hyemalis (n = 74), Melanitta fusca (n = 29), M. nigra (n = 15), and Somateria mollissima (n = 8). The following indices were established for the four species and for the Mergini tribe: KM/BM (as per cent body mass), KM/BL, and KM/SL. Additionally, allometric equations describing the relationships studied were developed for the tribe using mean kidney weights and body parameters of males and females of the species examined. The KM/BM indices for several anseriform tribes (i.e. Anserini, Anatini, Aythyini and Mergini), differing in food and feeding modes, were determined, based on the literature data and those obtained in this study. In addition, an allometric equation describing the kidney weight-body weight relationship in the Anseriformes order was developed as log KM = 0.797 log BM-1.346 (n = 22). The relative kidney size in the sea duck species studied showed significant intra- and interspecific differences. In addition, clear between-tribes differences in KM/BM were revealed. The highest value (1.57%) of the index is typical of the Mergini, grouping diving carnivorous sea ducks, while the lowest index (0.65%) is typical of the Anserini, a tribe which groups non-diving herbivorous birds.

Localization of sympathetic, parasympathetic and sensory neurons innervating the heart of the Beijing duck by means of the retrograde transport of horseradish peroxidase

Sympathetic, parasympathetic and sensory neurons were labeled by injections of horseradish peroxidase into various regions of the heart in 33 Beijing ducks. Sympathetic postganglionic neurons innervating the heart were located in the paravertebral ganglia C15 (C16 is the last cervical segment in the duck) to T3, especially in the ganglion T1. The coronary sulcus and ventricle were more abundantly innervated by sympathetic neurons than the atrium. The left side of the heart was preferentially innervated by sympathetic postganglionic neurons in the left side of paravertebral ganglia but the right side of the heart were equally supplied from the right and left ganglia. Within the medulla oblongata, the number of labeled vagal preganglionic neurons in the nucleus ambiguus was much greater than that in the dorsal motor nucleus of the vagus nerve. Labeled neurons of the nucleus ambiguus were found in many ducks injected into the coronary sulcus. Cardiac sensory neurons were observed in the dorsal root ganglia C15 to T2 (highest in the ganglion T1) and in the nodose and jugular ganglia of the vagus nerve. These labeled neurons probably form the afferent and efferent limbs of cardiac reflexes and control circulation in the Beijing duck.

Gross anatomy of the pancreatic lobes and ducts in six breeds of domestic ducks and six species of wild ducks in China

A previously unreported pancreatic duct was found by Liu (1989) in Pekin ducks. This duct has now been consistently found in six breeds of domestic ducks and six species of wild ducks in China. For purposes of Nomina Anatomica Avium it is hereby called the 'first pancreatic duct' (Ductus pancreaticus primus) since it enters the duodenum at or near the flexure where the descending duodenum becomes the ascending duodenum. All other pancreatic ducts enter the duodenum later, closer to where it joins the jejunum. This first pancreatic duct drains the caudal extremity of the dorsal lobe of the pancreas and can be easily exteriorized for experimental purposes. Within the parenchyma of the dorsal lobe of the pancreas this duct communicates with the dorsal pancreatic duct. In the present study of the gross anatomy of the pancreatic lobes of domestic and wild Chinese ducks we describe and illustrate variations in position and number of all biliary and pancreatic ducts.

Testosterone concentrations, testes weight and morphology of mule drakes (Muscovy drake x Khaki Campbell)

1. Mule ducks were produced by naturally mating Muscovy drakes and Khaki Campbell ducks. 2. Semen was collected from 6-month-old mule drakes via an artificial vagina. The fluid was clear without any spermatozoa or spermatids. 3. Testes from 27-week-old mule drakes were smaller in size than those of Khaki Campbell drakes but heavier than Muscovy males of the same age. Histological sections of these testes revealed that spermatogenesis was not complete. 4. Testosterone concentration in the mule drakes was higher than in Muscovy males but similar to Khaki Campbell drakes. 5. Mule drakes have strong sexual drives as a result of high concentrations of testosterone, but, because spermatogenesis is incomplete, their semen had no sperm.

The morphology of the ureter in the duck (Anas platyrhynchos)

The morphology of the ureter of the duck was investigated, using histological, SEM and TEM techniques. The inner perimeter, the total thickness of the ureteral wall and the thickness of each uretral layer were measured. The epithelium was tall columnar and pseudostratified along all the tracts of the ureter and showed a high muco-secretive activity. The lamina propria contained numerous capillaries and aggregates of leucocytes and macrophages. Throughout the lamina propria there was a dense plexus of nerves. Some denuded single nerve fibres were observed between the epithelial basal cells. A plexus of nerves was also observed in the tunica muscularis. The ostium cloacale ureteris opened on a well-developed papilla in the dorsal region of the urodeum. The total thickness of the ureteral wall, the thickness of the lamina propria and the tunica muscularis, and the inner perimeter progressively increased towards the ostium. The above observations suggest that the avian ureter plays an important role in the modification of the urine coming from medullary cones, and in emission of the urine into the cloaca.

Cerebellar and spinal projections of the coeruleus complex in the duck: a fluorescent retrograde double-labeling study

The double fluorescent retrograde tracing technique was used to identify, within the coeruleus complex (Co complex) of the duck, the nerve cells projecting to the cerebellar cortex and to the spinal cord. This technique was also used to investigate the possibility that the cerebellar and spinal projections of the Co complex are collaterals of the same axons. In the same animal, nuclear Diamidino yellow dihydrochloride (DY) fluorescent tracer was placed into the cerebellar cortex of folia V-VII, and cytoplasmic fluorescent Fast blue (FB) dye was injected into C3-C4 spinal cord segments. FB labeled multipolar somata and DY fluorescent nuclei were intermingled within the dorsal caudal region of the locus coeruleus (LCo) and within the dorsal division of the nucleus subcoeruleus (dSCo). Moreover, in the LCo, a low proportion of double-labeled neurons (about 3-4% of labelings) was evidenced among single-labeled neurons. In the ventral division of the nucleus subcoeruleus (vSCo), occasional DY labeled nuclei were found, whereas FB-labeled cells were frequently present. The present findings reveal the location of the coeruleocerebellar and coeruleospinal projecting neurons within the Co complex of the duck. They are intermingled in the caudal portion of the LCo and along the rostrocaudal extent of the subjacent dSco. The LCo and the dSCo are the major source of the projections to the folia V-VII, whereas the vSCo contributes very slightly to the innervation of the cerebellar injected areas. Moreover, the double-labeling study demonstrates that in the duck a low percentage of neurons within the ventrolateral portion of the caudal region of the LCo projects both to the cerebellar cortex of folia V-VII and to C3-C4 spinal cord segments via collaterals. Therefore, these neurons simultaneously influence the cerebellar cortex and spinal cord. The possibility that the projections studied are noradrenergic and that they play a role in feeding is discussed.

[Preliminary examinations on the effects of the breed characteristic feature "feather crest" on skull and brain anatomy of domestic ducks (Anas platyrhynchos f. dom.)]

As mentioned in older sources, the crested breed of the domestic duck is described as variety with high pre- and postnatal mortalities, malformations in skull and brain anatomy, and several central nervous deficiencies in affected birds. Therefore this breed is to be called defective and abnormal in the sense of section 11b of the German protection of animals legislation. Poultry fanciers reject these findings as incorrect, but accurate scientific examinations that bear out this allegation are not available. Preliminary examinations have demonstrated that brain and skull anatomy of living animals can be described by using non-invasive diagnostic techniques (magnet-resonance-imaging, computerized tomography, radiography). The use of this progressive methods enables to expressive findings on present stocks of domestic ducks. Many of the test animals investigated in preliminary examinations by using magnet-resonance-imaging and radiography showed abnormal tissue deposits in the tentorium cerebelli, meningo-encephalocele, cranial malformations, and variable bone formations in the thickened hypodermis of the crest. If crested ducks are mated against each other, numerous offspring show malformations of upper beak and cranium, encephalocele, as well as craniopagal parasites in form of rudimentary legs.

Posthatching myofiber development in the M. pectoralis of White Pekin Ducks

BACKGROUND

A posthatching transformation of fast-twitch oxidative-glycolytic (FTO) to fast-twitch glycolytic (FTG) fibers in the breast muscle in domestic chickens and turkeys is well documented. There is, however, no information on the situation in Anseriformes having a M. pectoralis with a mixed fiber composition in adults. Differences in the growth of the different fiber types were reported for some muscles in ducks as well as in other birds. They are examined in the main flight muscle using growth curve analysis, until now mostly applied to the analysis of overall growth.

METHODS

Biopsies were taken longitudinally from the M. pectoralis, Pars thoracica, of 40 White Pekin Ducks at 11 different ages from hatching through day 146. The samples were processed for a combination of nicotinamide adenine dinucleotide tetrazolium reductase and myosin adenosine triphosphatase after acid preincubation at pH 4.1. Mean fiber diameter was determined for the different fiber types in relation to age. The Janoschek growth curve was fitted to these values.

RESULTS

FTG fibers were first detected at 20 days of age. Thereafter, the fiber composition hardly changed. When distinguishable by enzyme histochemistry, FTG fibers were already larger in diameter than FTO. There were only gradual differences in the growth pattern. FTG fibers, however, showed much higher absolute, percentage, and relative growth rates. The radial growth of myofibers is slow when compared to other one-dimensional measurements.

CONCLUSIONS

Fiber transformation seems to take place within a short age period. However, further studies are necessary to discriminate effects resulting from sample depth. FTG fibers are presumably recruited from those FTO fibers that show higher growth rates. Growth curve analysis, more frequently used in gross morphological studies, provides an analytical tool for evaluating growth processes of cells and tissues as well. Fiber size differences are mainly due to a higher growth rate in FTG fibers, whereas the growth patterns show only minor differences.

The structure of the interstitial tissue of the active and resting avian testis

The interstitial tissue of the testis was studied in gonadally active and gonadally inactive domestic fowl (Gallus gallus domesticus), guinea-fowl (Numida meleagris), duck (Anas platyrhynchos) and Japanese quail (Coturnix coturnix japonica). Gonadal inactivity in the fowl was induced by a single subcutaneous injection of 50 mg oestradiol benzoate. The structure of this tissue was similar in all the birds studied. Lymphatic vessels were mostly thin and meandered between the peritubular tissue peripherally and the centrally located blood vessels, Leydig cells and macrophages. The basal lamina rested on a closely associated homogeneous microfibrillar layer free of collagen fibres. The myofibroblast layer was several cells thick, and quite compact. The basal lamina of gonadally resting birds was highly irregular, relatively electron-dense, contained electron-lucent globules, and sent numerous finger-like processes or plicae into the seminiferous epithelium, particularly into the Sertoli cells. The Leydig cells were few but typical in structure. In gonadally inactive birds they accumulated lipid droplets, dense heterogeneous bodies, probably lysosomes, and appeared to degenerate. The avian testicular interstitium is similar to that of the human and cat in possessing a multi-layered myofibroblast component, and to that of the rodent in possessing a small number of Leydig cells, as well as in the location of the lymphatic vessels. Thus the bird combines characteristics of the interstitium found variably in mammals.

Central connections of the nucleus mesencephalicus nervi trigemini in the mallard (Anas platyrhynchos L.)

BACKGROUND

In the mallard duck, functionally distinct groups of jaw muscles are each innervated by a different subnucleus of the main trigeminal (mV) or facial (mVII) motor nucleus. The other subnuclei of mV and mVII innervate several head muscles, including lingual muscles. The reticular premotor cells of the trigeminal and facial jaw motor subnuclei occupy different areas in the parvocellular reticular formation (RPc). The cell bodies of jaw muscle spindle afferents are situated in the mesencephalic nucleus (MesV). In the present study, the central connections of MesV with jaw motor subnuclei and their premotor areas are investigated.

METHODS

In a first series of experiments, horseradish peroxidase (HRP) injections were made in electrophysiologically identified trigeminal and facial subnuclei. In a second series of experiments, HRP was delivered iontophoretically at different parts of RPc. Anterograde tracing with tritiated leucine was used to confirm the central connections of MesV. Double labeling with fluorescent tracers was used to investigate whether MesV collaterals reach both the rostral and caudal parts of RPc.

RESULTS

MesV projects to only two of the five different subnuclei of the trigeminal motor nucleus. The subnuclei that receive spindle afferents innervate jaw adductor muscles (mV2) or pro- and retractors of the mandible (pterygoid muscles; mV1). The three other subnuclei innervate jaw-opener muscles or other head muscles. MesV fibers also project to the rostral part of the dorsolateral RPc (RPcdl), which serves as a premotor area for the motor subnuclei of adductor and pterygoid muscles. The intermediate part of RPcdl does not contain premotor cells of mV or mVII, and a clear projection of MesV to this area is absent. The caudal part of RPcdl projects to the mV and mVII subnuclei that innervate jaw-opener muscles. This part of RPc receives a projection from the same MesV cells as the rostral RPcdl. The MesV projection to RPc does not include premotor cells of mV and mVII in the ventromedial part of RPc (RPcvm).

CONCLUSIONS

Spindle afferents from jaw-closer muscles project only to mV subnuclei innervating jaw-closer muscles (mV1, mV2) and to a population of premotor cells in the rostral RPcdl that innervates these subnuclei. The mixed population of premotor cells in RPcvm, which innervates both jaw-opener and jaw-closer subnuclei, does not receive a MesV projection. However, a premotor area for jaw-opener subnuclei in the caudal part of RPcdl does receive MesV input and may serve as a relay through which proprioceptive information from jaw closer spindles can reach jaw opener muscles.